Materials

26 pages, 66555 KiB

Open AccessArticle

Peculiar Porous Aluminum Oxide Films Produced via Electrochemical Anodizing in Malonic Acid Solution with Arsenazo-I Additive

by Alexander Poznyak, Gerhard Knörnschild, Anatoly Karoza, Małgorzata Norek and Andrei Pligovka

Materials 2021, 14(17), 5118; https://doi.org/10.3390/ma14175118 - 6 Sep 2021

Cited by 13 | Viewed by 2663

Abstract

The influence of arsenazo-I additive on electrochemical anodizing of pure aluminum foil in malonic acid was studied. Aluminum dissolution increased with increasing arsenazo-I concentration. The addition of arsenazo-I also led to an increase in the volume expansion factor up to 2.3 due to [...] Read more.

The influence of arsenazo-I additive on electrochemical anodizing of pure aluminum foil in malonic acid was studied. Aluminum dissolution increased with increasing arsenazo-I concentration. The addition of arsenazo-I also led to an increase in the volume expansion factor up to 2.3 due to the incorporation of organic compounds and an increased number of hydroxyl groups in the porous aluminum oxide film. At a current density of 15 mA·cm⁻² and an arsenazo-I concentration 3.5 g·L⁻¹, the carbon content in the anodic alumina of 49 at. % was achieved. An increase in the current density and concentration of arsenazo-I caused the formation of an arsenic-containing compound with the formula Na_1,5Al₂(OH)_4,5(AsO₄)₃·7H₂O in the porous aluminum oxide film phase. These film modifications cause a higher number of defects and, thus, increase the ionic conductivity, leading to a reduced electric field in galvanostatic anodizing tests. A self-adjusting growth mechanism, which leads to a higher degree of self-ordering in the arsenazo-free electrolyte, is not operative under the same conditions when arsenazo-I is added. Instead, a dielectric breakdown mechanism was observed, which caused the disordered porous aluminum oxide film structure. Full article

(This article belongs to the Special Issue Anodizing of Metals: From Corrosion Protection to Advances in Nanotechnology and Emerging Applications)

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20 pages, 8016 KiB

Open AccessReview

SHS-Derived Powders by Reactions’ Coupling as Primary Products for Subsequent Consolidation

by Sofiya Aydinyan, Suren Kharatyan and Irina Hussainova

Materials 2021, 14(17), 5117; https://doi.org/10.3390/ma14175117 - 6 Sep 2021

Cited by 7 | Viewed by 2329

Abstract

The capability of self-propagating high-temperature synthesis (SHS) to produce powders that are characterized by a high sintering ability, owing to high heating and cooling rates inherent to the exothermic reaction, is of a special interest for the industry. In particular, SHS-derived powders comprise [...] Read more.

The capability of self-propagating high-temperature synthesis (SHS) to produce powders that are characterized by a high sintering ability, owing to high heating and cooling rates inherent to the exothermic reaction, is of a special interest for the industry. In particular, SHS-derived powders comprise a significant defect concentration in order to effectively enhance the mass transfer processes during the sintering, which allows for the successful consolidation of difficult-to-sinter materials at relatively low sintering temperatures. From this perspective, the design of precursors suitable for sintering, synthesis in a controlled temperature regime and the optimization of geometrical and structural parameters of SHS powders as a potential feedstock for the consolidation is of key importance. Here, we report on the comparative studies concerning the SHS processing of composites for advanced powder metallurgy techniques. The synthesis and sintering peculiarities of the SHS through coupled reactions in the Me’O₃(WO₃,MoO₃)-Me’’O(CuO,NiO)-Mg-C, Ti-B-Al₁₂Mg₁₇ systems are comparatively reviewed. The SHS coupling approach was used for the preparation of powders with a tuned degree of fineness (a high specific surface area of particles), a high-homogeneity and a controllable distribution of elements via both the regulation of the thermal regime of combustion in a wide range and the matching of the thermal and kinetic requirements of two interconnected reactions. Microstructural features of the powder feedstock greatly contributed to the subsequent consolidation process. Full article

(This article belongs to the Special Issue Collection of Papers in Materials Science from Estonia)

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27 pages, 74594 KiB

Open AccessReview

Microorganism, Carriers, and Immobilization Methods of the Microbial Self-Healing Cement-Based Composites: A Review

by Li’an Shen, Wenlu Yu, Lin Li, Tong Zhang, Ismail Yusuf Abshir, Pingping Luo and Zhuangzhuang Liu

Materials 2021, 14(17), 5116; https://doi.org/10.3390/ma14175116 - 6 Sep 2021

Cited by 24 | Viewed by 4333

Abstract

Low tensile strength, poor elastic modulus, and complex concrete cracking work condition are almost unavoidable due to the intrinsic brittleness. To deal with concrete maintenance and durability, microbial self-healing concretes have been rapidly developed and widely applied recently. The microbial self-healing can specifically [...] Read more.

Low tensile strength, poor elastic modulus, and complex concrete cracking work condition are almost unavoidable due to the intrinsic brittleness. To deal with concrete maintenance and durability, microbial self-healing concretes have been rapidly developed and widely applied recently. The microbial self-healing can specifically patch fractures as well as boost the concrete structure’s capacity, durability, and permeability. This paper presents the state-of-the-art in the microbe induced self-healing in cement-based composites. The microorganism and carriers were classified according to the working theory and repair effects. Additionally, the precise efficiency and effect of various technologies are also evaluated for microbial immobilization. Based on the literature review and summary from the perspective of microorganism, carriers, and immobilization methods, challenges and further works are discussed. Full article

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

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29 pages, 15887 KiB

Open AccessArticle

Methane and Carbon Dioxide Hydrate Formation and Dissociation in Presence of a Pure Quartz Porous Framework Impregnated with CuSn12 Metallic Powder: An Experimental Report

by Alberto Maria Gambelli, Giulia Stornelli, Andrea Di Schino and Federico Rossi

Materials 2021, 14(17), 5115; https://doi.org/10.3390/ma14175115 - 6 Sep 2021

Cited by 10 | Viewed by 1947

Abstract

Hydrate formation and dissociation processes were carried out in the presence of a pure quartz porous medium impregnated with a metallic powder made with a CuSn12 alloy. Experiments were firstly made in the absence of that powder; then, different concentrations were added to [...] Read more.

Hydrate formation and dissociation processes were carried out in the presence of a pure quartz porous medium impregnated with a metallic powder made with a CuSn12 alloy. Experiments were firstly made in the absence of that powder; then, different concentrations were added to the porous medium: 4.23 wt.%, 18.01 wt.%, and 30.66 wt.%. Then, the hydrate dissociation values were compared with those present in the literature. The porous medium was found to act as an inhibitor in the presence of carbon dioxide, while it did not alter methane hydrate, whose formation proceeded similarly to the ideal trend. The addition of CuSn12 promoted the process significantly. In particular, in concentrations of up to 18.01 wt.%, CO₂ hydrate formed at milder conditions until it moved below the ideal equilibrium curve. For methane, the addition of 30.66 wt.% of powder significantly reduced the pressure required to form hydrate, but in every case, dissociation values remained below the ideal equilibrium curve. Full article

(This article belongs to the Special Issue Chemical and Structural Engineering of Nanomaterials)

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19 pages, 16846 KiB

Open AccessArticle

Imaging of Increasing Damage in Steel Plates Using Lamb Waves and Ultrasound Computed Tomography

by Monika Zielińska and Magdalena Rucka

Materials 2021, 14(17), 5114; https://doi.org/10.3390/ma14175114 - 6 Sep 2021

Cited by 12 | Viewed by 2584

Abstract

This paper concerns the inspection of steel plates, with particular emphasis on the assessment of increasing damage. Non-destructive tests were performed on four plates, one of which was undamaged, while the remaining three had defects in the form of circular holes with diameters [...] Read more.

This paper concerns the inspection of steel plates, with particular emphasis on the assessment of increasing damage. Non-destructive tests were performed on four plates, one of which was undamaged, while the remaining three had defects in the form of circular holes with diameters of 2, 5 and 10 cm. Guided Lamb waves were used in the research, and the image reconstruction was performed using ultrasound computed tomography. The damage size was estimated by tracking the real course of rays and densifying the pixel grid into which the object was divided. The results showed the great potential of ultrasound tomography in detecting defects in steel elements, together with the possibility of estimating damage size. Full article

(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))

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27 pages, 3501 KiB

Open AccessEditor’s ChoiceReview

Review on the Integration of Microelectronics for E-Textile

by Abdella Ahmmed Simegnaw, Benny Malengier, Gideon Rotich, Melkie Getnet Tadesse and Lieva Van Langenhove

Materials 2021, 14(17), 5113; https://doi.org/10.3390/ma14175113 - 6 Sep 2021

Cited by 61 | Viewed by 7197

Abstract

Modern electronic textiles are moving towards flexible wearable textiles, so-called e-textiles that have micro-electronic elements embedded onto the textile fabric that can be used for varied classes of functionalities. There are different methods of integrating rigid microelectronic components into/onto textiles for the development [...] Read more.

Modern electronic textiles are moving towards flexible wearable textiles, so-called e-textiles that have micro-electronic elements embedded onto the textile fabric that can be used for varied classes of functionalities. There are different methods of integrating rigid microelectronic components into/onto textiles for the development of smart textiles, which include, but are not limited to, physical, mechanical, and chemical approaches. The integration systems must satisfy being flexible, lightweight, stretchable, and washable to offer a superior usability, comfortability, and non-intrusiveness. Furthermore, the resulting wearable garment needs to be breathable. In this review work, three levels of integration of the microelectronics into/onto the textile structures are discussed, the textile-adapted, the textile-integrated, and the textile-based integration. The textile-integrated and the textile-adapted e-textiles have failed to efficiently meet being flexible and washable. To overcome the above problems, researchers studied the integration of microelectronics into/onto textile at fiber or yarn level applying various mechanisms. Hence, a new method of integration, textile-based, has risen to the challenge due to the flexibility and washability advantages of the ultimate product. In general, the aim of this review is to provide a complete overview of the different interconnection methods of electronic components into/onto textile substrate. Full article

(This article belongs to the Special Issue Smart Textile Materials and Fabric-Based Wearable Devices)

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14 pages, 12687 KiB

Open AccessArticle

Compressive Behavior of Al-TiB₂ Composite Foams Fabricated under Increased Pressure

by Yang Yu, Zhuokun Cao, Jiaqi Wang, Ganfeng Tu and Yongliang Mu

Materials 2021, 14(17), 5112; https://doi.org/10.3390/ma14175112 - 6 Sep 2021

Cited by 4 | Viewed by 1627

Abstract

The application of increased pressure was used as a strategy to investigate the effect of different cell structures on the mechanical properties of Al-TiB₂ composite foams. In situ Al-xTiB₂ (x = 5, 10 wt.%) composites were foamed under three different pressures [...] Read more.

The application of increased pressure was used as a strategy to investigate the effect of different cell structures on the mechanical properties of Al-TiB₂ composite foams. In situ Al-xTiB₂ (x = 5, 10 wt.%) composites were foamed under three different pressures (0.1 MPa, 0.24 MPa, 0.4 MPa) through the liquid melt route. The macro-structure of the composite foams was analyzed in terms of cell size distribution measured by X-ray microcomputed tomography (micro-CT). It was found that the mean cell size decreases, and the cell size distribution range narrows with increasing pressure. Uniaxial compression tests revealed that the stress fluctuation (R_sd) of 10TiB₂ foams is larger than that of 5TiB₂ foams under the same pressure. Moreover, cell size refinement causes the simultaneous deformation of multi-layer cells, which leads to an enhancement in the energy absorption efficiency and specific energy absorption. The comparison of experimental data with theoretical predictions (G&A model) is discussed. Full article

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12 pages, 7917 KiB

Open AccessArticle

Position Control and Force Estimation Method for Surgical Forceps Using SMA Actuators and Sensors

by Dennis Braun, David Weik, Sophia Elsner, Sandra Hunger, Michael Werner and Welf-Guntram Drossel

Materials 2021, 14(17), 5111; https://doi.org/10.3390/ma14175111 - 6 Sep 2021

Cited by 9 | Viewed by 2946

Abstract

Minimally invasive surgery is increasingly used in many medical operations because of the benefits for the patients. However, for the surgeons, accessing the situs through a small incision or natural orifice comes with a reduction of the degrees of freedom of the instrument. [...] Read more.

Minimally invasive surgery is increasingly used in many medical operations because of the benefits for the patients. However, for the surgeons, accessing the situs through a small incision or natural orifice comes with a reduction of the degrees of freedom of the instrument. Due to friction of the mechanical coupling, the haptic feedback lacks sensitivity that could lead to damage of the tissue. The approach of this work to overcome these problems is to develop a control concept for position control and force estimation with shape memory alloys (SMA) which could offer haptic feedback in a novel handheld instrument. The concept aims to bridge the gap between manually actuated laparoscopic instruments and surgical robots. Nickel-titanium shape memory alloys are used for actuation because of their high specific energy density. The work includes the manufacturing of a functional model as a proof of concept comprising the development of a suitable forceps mechanism and electronic circuit for position control and gripping force measurement, as well as designing an ergonomic user interface with haptic force feedback. Full article

(This article belongs to the Special Issue Design, Characterization and Novel Applications of Shape Memory Alloys)

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15 pages, 2943 KiB

Open AccessArticle

Experimental Investigations on Electric-Field-Induced Crystallization in Erythritol

by Jean-Luc Dauvergne, Artem Nikulin, Stefania Doppiu and Elena Palomo del Barrio

Materials 2021, 14(17), 5110; https://doi.org/10.3390/ma14175110 - 6 Sep 2021

Cited by 6 | Viewed by 2270

Abstract

The objective of this experimental study was to develop a method to induce crystallization of sugar alcohols using an electric field for its future implementation in latent heat thermal energy storage systems. To better understand the mechanisms behind this approach, the first step [...] Read more.

The objective of this experimental study was to develop a method to induce crystallization of sugar alcohols using an electric field for its future implementation in latent heat thermal energy storage systems. To better understand the mechanisms behind this approach, the first step of this work was dedicated to the replication, continuation, and consolidation of promising results on erythritol reported by another research group. In the second step, a second experimental configuration, previously used to electrically control the supercooling of other phase change materials, was tested with the same sugar alcohol. For both configurations, the influence of the type of current (DC and AC at different frequencies), its amplitude, and time of exposure were studied. However, none of these tests allowed influencing the crystallization of erythritol. Even if surprising at first glance, the difficulty in reproducing experiments and interpreting the results is not new in the field of electric-field-induced crystallization, as shown in particular by the abundant literature reviews concerning water. Currently, to the best of our knowledge, we consider that electric fields could be an attractive option to initiate and accelerate the crystallization of erythritol, but this solution must be considered with caution. Full article

(This article belongs to the Special Issue Advanced Materials for Thermal Energy Storage)

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16 pages, 1999 KiB

Open AccessArticle

Comparison of NSGA-II, MOALO and MODA for Multi-Objective Optimization of Micro-Machining Processes

by Milan Joshi, Ranjan Kumar Ghadai, S. Madhu, Kanak Kalita and Xiao-Zhi Gao

Materials 2021, 14(17), 5109; https://doi.org/10.3390/ma14175109 - 6 Sep 2021

Cited by 32 | Viewed by 3325

Abstract

The popularity of micro-machining is rapidly increasing due to the growing demands for miniature products. Among different micro-machining approaches, micro-turning and micro-milling are widely used in the manufacturing industry. The various cutting parameters of micro-turning and micro-milling has a significant effect on the [...] Read more.

The popularity of micro-machining is rapidly increasing due to the growing demands for miniature products. Among different micro-machining approaches, micro-turning and micro-milling are widely used in the manufacturing industry. The various cutting parameters of micro-turning and micro-milling has a significant effect on the machining performance. Thus, it is essential that the cutting parameters are optimized to obtain the most from the machining process. However, it is often seen that many machining objectives have conflicting parameter settings. For example, generally, a high material removal rate (MRR) is accompanied by high surface roughness (SR). In this paper, metaheuristic multi-objective optimization algorithms are utilized to generate Pareto optimal solutions for micro-turning and micro-milling applications. A comparative study is carried out to assess the performance of non-dominated sorting genetic algorithm II (NSGA-II), multi-objective ant lion optimization (MOALO) and multi-objective dragonfly optimization (MODA) in micro-machining applications. The complex proportional assessment (COPRAS) method is used to compare the NSGA-II, MOALO and MODA generated Pareto solutions. Full article

(This article belongs to the Special Issue Numerical Modeling for Simulation of Different Processes in Manufacturing)

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14 pages, 1122 KiB

Open AccessArticle

Harmonic Extraction in Graphene: Monte Carlo Analysis of the Substrate Influence

by Elena Pascual, José M. Iglesias, María J. Martín and Raúl Rengel

Materials 2021, 14(17), 5108; https://doi.org/10.3390/ma14175108 - 6 Sep 2021

Cited by 2 | Viewed by 1649

Abstract

Graphene on different substrates, such as SiO

_{2}

, h-BN and Al

_{2}

O

_{3}

, has been subjected to oscillatory electric fields to analyse the response of the carriers in order to explore the generation of terahertz radiation by means of high-order [...] Read more.

Graphene on different substrates, such as SiO

_{2}

, h-BN and Al

_{2}

O

_{3}

, has been subjected to oscillatory electric fields to analyse the response of the carriers in order to explore the generation of terahertz radiation by means of high-order harmonic extraction. The properties of the ensemble Monte Carlo simulator employed for such study have allowed us to evaluate the high-order harmonic intensity and the spectral density of velocity fluctuations under different amplitudes of the periodic electric field, proving that strong field conditions are preferable for the established goal. Furthermore, by comparison of both harmonic intensity and noise level, the threshold bandwidth for harmonic extraction has been determined. The results have shown that graphene on h-BN presents the best featuring of the cases under analysis and that in comparison to III–V semiconductors, it is a very good option for high-order harmonic extraction under AC electric fields with large amplitudes. Full article

(This article belongs to the Special Issue Advances in Graphene and Other Novel Two-Dimensional Materials for Electronic Applications)

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10 pages, 2689 KiB

Open AccessArticle

Microstructure Evolution in He-Implanted Si at 600 °C Followed by 1000 °C Annealing

by Zhen Yang, Zhiping Zou, Zeyang Zhang, Yubo Xing and Tao Wang

Materials 2021, 14(17), 5107; https://doi.org/10.3390/ma14175107 - 6 Sep 2021

Cited by 3 | Viewed by 1985

Abstract

Si single crystal was implanted with 230 keV He⁺ ions to a fluence of 5 × 10¹⁶/cm² at 600 °C. The structural defects in Si implanted with He at 600 °C and then annealed at 1000 °C were investigated [...] Read more.

Si single crystal was implanted with 230 keV He⁺ ions to a fluence of 5 × 10¹⁶/cm² at 600 °C. The structural defects in Si implanted with He at 600 °C and then annealed at 1000 °C were investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The microstructure of an as-implanted sample is provided for comparison. After annealing, rod-like defects were diminished, while tangled dislocations and large dislocation loops appeared. Dislocation lines trapped by cavities were directly observed. The cavities remained stable except for a transition of shape, from octahedron to tetrakaidecahedron. Stacking-fault tetrahedrons were found simultaneously. Cavity growth was independent of dislocations. The evolution of observed lattice defects is discussed. Full article

(This article belongs to the Special Issue Experiment and Calculation Simulation to Study Hydrogen-Helium Effect Mechanism in Materials)

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14 pages, 3286 KiB

Open AccessArticle

A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations

by Alan A. Camberg, Tobias Erhart and Thomas Tröster

Materials 2021, 14(17), 5106; https://doi.org/10.3390/ma14175106 - 6 Sep 2021

Cited by 2 | Viewed by 3135

Abstract

Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow [...] Read more.

Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow the assessment of critical forming strains for steady temperatures. For this reason, a temperature-dependent extension of the well-established GISSMO (Generalized Incremental Stress State Dependent Damage Model) fracture indicator framework is developed by the authors to predict forming failures under non-isothermal conditions. In this paper, a general approach to combine several isothermal FLCs within the temperature-extended GISSMO model into a temperature-dependent forming limit surface is investigated. The general capabilities of the model are tested in a coupled thermo-mechanical FEA using the example of warm forming of an AA5182-O sheet metal cross-die cup. The obtained results are then compared with state of the art of evaluation methods. By taking the strain and temperature path into account, GISSMO predicts greater drawing depths by up to

20 %

than established methods. In this way the forming and so the lightweight potential of sheet metal parts can by fully exploited. Moreover, the risk and locus of failure can be evaluated directly on the part geometry by a contour plot. An additional advantage of the GISSMO model is the applicability for low triaxialities as well as the possibility to predict the materials behavior beyond necking up to ductile fracture. Full article

(This article belongs to the Special Issue Metal Forming and Forging)

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10 pages, 1426 KiB

Open AccessArticle

4H-SiC Schottky Barrier Diodes for Efficient Thermal Neutron Detection

by Robert Bernat, Luka Bakrač, Vladimir Radulović, Luka Snoj, Takahiro Makino, Takeshi Ohshima, Željko Pastuović and Ivana Capan

Materials 2021, 14(17), 5105; https://doi.org/10.3390/ma14175105 - 6 Sep 2021

Cited by 6 | Viewed by 2752

Abstract

In this work, we present the improved efficiency of 4H-SiC Schottky barrier diodes-based detectors equipped with the thermal neutron converters. This is achieved by optimizing the thermal neutron converter thicknesses. Simulations of the optimal thickness of thermal neutron converters have been performed using [...] Read more.

In this work, we present the improved efficiency of 4H-SiC Schottky barrier diodes-based detectors equipped with the thermal neutron converters. This is achieved by optimizing the thermal neutron converter thicknesses. Simulations of the optimal thickness of thermal neutron converters have been performed using two Monte Carlo codes (Monte Carlo N–Particle Transport Code and Stopping and Range of Ions in Matter). We have used ⁶LiF and ¹⁰B₄C for the thermal neutron converter material. We have achieved the thermal neutron efficiency of 4.67% and 2.24% with ⁶LiF and ¹⁰B₄C thermal neutron converters, respectively. Full article

(This article belongs to the Special Issue SiC Based Technology for High Power Electronics)

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18 pages, 5169 KiB

Open AccessReview

Potential of Carbon-Based Nanocomposites for Dental Tissue Engineering and Regeneration

by Moon Sung Kang, Hee Jeong Jang, Seok Hyun Lee, Ji Eun Lee, Hyo Jung Jo, Seung Jo Jeong, Bongju Kim and Dong-Wook Han

Materials 2021, 14(17), 5104; https://doi.org/10.3390/ma14175104 - 6 Sep 2021

Cited by 9 | Viewed by 3188

Abstract

While conventional dental implants focus on mechanical properties, recent advances in functional carbon nanomaterials (CNMs) accelerated the facilitation of functionalities including osteoinduction, osteoconduction, and osseointegration. The surface functionalization with CNMs in dental implants has emerged as a novel strategy for reinforcement and as [...] Read more.

While conventional dental implants focus on mechanical properties, recent advances in functional carbon nanomaterials (CNMs) accelerated the facilitation of functionalities including osteoinduction, osteoconduction, and osseointegration. The surface functionalization with CNMs in dental implants has emerged as a novel strategy for reinforcement and as a bioactive cue due to their potential for mechanical reinforcing, osseointegration, and antimicrobial properties. Numerous developments in the fabrication and biological studies of CNMs have provided various opportunities to expand their application to dental regeneration and restoration. In this review, we discuss the advances in novel dental implants with CNMs in terms of tissue engineering, including material combination, coating strategies, and biofunctionalities. We present a brief overview of recent findings and progression in the research to show the promising aspect of CNMs for dental implant application. In conclusion, it is shown that further development of surface functionalization with CNMs may provide innovative results with clinical potential for improved osseointegration after implantation. Full article

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

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14 pages, 509 KiB

Open AccessArticle

The Expression of Allele Changes in NLRP3 (rs35829419) and IL-1β (+3954) Gene Polymorphisms in Periodontitis and Coronary Artery Disease

by Jaideep Mahendra, Abirami Nayaki Rao, Little Mahendra, Mohammed E. Sayed, Maryam H. Mugri, Thodur Madapusi Balaji, Saranya Varadarajan, Raghunathan Jagannathan, Sruthi Srinivasan, Hosam Ali Baeshen, Reji Mathew and Shankargouda Patil

Materials 2021, 14(17), 5103; https://doi.org/10.3390/ma14175103 - 6 Sep 2021

Cited by 6 | Viewed by 2267

Abstract

Background: Inflammasomes have been shown to play a pivotal role in periodontal disease pathogenesis. However, their role in periodontitis subjects with coronary heart disease remains unclear. This study aimed to obtain the expression of NLRP3 (rs35829419) and IL-1β (+3954) gene polymorphisms in the [...] Read more.

Background: Inflammasomes have been shown to play a pivotal role in periodontal disease pathogenesis. However, their role in periodontitis subjects with coronary heart disease remains unclear. This study aimed to obtain the expression of NLRP3 (rs35829419) and IL-1β (+3954) gene polymorphisms in the subgingival plaque and blood samples of generalized periodontitis (GP) subjects with and without coronary heart disease (CHD). Methods: A total of 70 subjects were grouped into two; GP and GP with CHD. Demographic variables and periodontal and cardiac parameters were recorded from both the groups. Subgingival plaque and blood samples were obtained from both the groups and were further subjected to the identification of NLRP3 (rs35829419) and IL-1β (+3954) expression and allele change using a conventional polymerase chain reaction (PCR) and gene sequencing (Sanger’s method). Results: Amongst the demographic variables, age and monthly income were statistically significant between the two groups. Plaque index (PI), clinical attachment level (CAL), high-density lipoprotein (HDL), and low density-lipoprotein (LDL) exhibited statistically significant levels between the two groups. The NLRP3 (rs35829419) and IL-1β (+3954) genes showed a statistically significant association with allele change (frequency) among the groups. The general comparison of all the parameters with the allele change of NLRP3 (rs35829419) and IL-1β (+3954) in the subgingival plaque and blood samples showed statistically significant associations among the two groups. Conclusion: The present study highlighted an allele change in IL-1β (+3954) gene polymorphisms which may play an important role in the pathogenesis of periodontitis and coronary heart disease. Full article

(This article belongs to the Special Issue Advances in Periodontics and Restorative Dental Materials)

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22 pages, 6032 KiB

Open AccessArticle

Thermally Treated Waste Silt as Filler in Geopolymer Cement

by Abbas Solouki, Alireza Fathollahi, Giovanni Viscomi, Piergiorgio Tataranni, Giovanni Valdrè, Stephen J. Coupe and Cesare Sangiorgi

Materials 2021, 14(17), 5102; https://doi.org/10.3390/ma14175102 - 6 Sep 2021

Cited by 9 | Viewed by 2838

Abstract

This study aims to investigate the feasibility of including silt, a by-product of limestone aggregate production, as a filler in geopolymer cement. Two separate phases were planned: The first phase aimed to determine the optimum calcination conditions of the waste silt obtained from [...] Read more.

This study aims to investigate the feasibility of including silt, a by-product of limestone aggregate production, as a filler in geopolymer cement. Two separate phases were planned: The first phase aimed to determine the optimum calcination conditions of the waste silt obtained from Società Azionaria Prodotti Asfaltico Bituminosi Affini (S.A.P.A.B.A. s.r.l.). A Design of Experiment (DOE) was produced, and raw silt was calcined accordingly. Geopolymer cement mixtures were made with sodium or potassium alkali solutions and were tested for compressive strength and leaching. Higher calcination temperatures showed better compressive strength, regardless of liquid type. By considering the compressive strength, leaching, and X-ray diffraction (XRD) analysis, the optimum calcination temperature and time was selected as 750 °C for 2 h. The second phase focused on determining the optimum amount of silt (%) that could be used in a geopolymer cement mixture. The results suggested that the addition of about 55% of silt (total solid weight) as filler can improve the compressive strength of geopolymers made with Na or K liquid activators. Based on the leaching test, the cumulative concentrations of the released trace elements from the geopolymer specimens into the leachant were lower than the thresholds for European standards. Full article

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

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9 pages, 2252 KiB

Open AccessArticle

Magnetic Properties of Novel Layered Disulfides CuCr0.99Ln0.01S2 (Ln = La…Lu)

by Evgeniy V. Korotaev, Mikhail M. Syrokvashin, Irina Yu. Filatova and Valentina V. Zvereva

Materials 2021, 14(17), 5101; https://doi.org/10.3390/ma14175101 - 6 Sep 2021

Cited by 8 | Viewed by 1862

Abstract

The comprehensive study of the lanthanide-doped solid solutions CuCr_0.99Ln_0.01S₂ (Ln = La…Lu) magnetic properties was carried out using static magnetochemistry and differential scanning calorimetry techniques. It was shown that magnetic properties of CuCr_0.99Ln_0.01S₂ [...] Read more.

The comprehensive study of the lanthanide-doped solid solutions CuCr_0.99Ln_0.01S₂ (Ln = La…Lu) magnetic properties was carried out using static magnetochemistry and differential scanning calorimetry techniques. It was shown that magnetic properties of CuCr_0.99Ln_0.01S₂ are significantly affected by the magnetic properties of the lanthanide ion. The magnetic susceptibility and the effective magnetic moment were found to deviate from the Curie-Weiss law in the temperature 90 K below and 50 K above the order-disorder transition at 695 K. The observed behavior of the temperature dependence of the effective magnetic moment in the order-disorder transition temperature region was described as a result of copper atoms redistribution over different types of the crystallographic sites. Full article

(This article belongs to the Special Issue Multifunction Materials, Interfaces, and Composites: Design and Applications)

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16 pages, 28795 KiB

Open AccessArticle

Performance of MoS₂/Zr Composite Coatings at Different Deposition Temperatures

by Wenlong Song, Kai Sun, Guangming Zhao, Long Zhu, Shoujun Wang and Tianya Li

Materials 2021, 14(17), 5100; https://doi.org/10.3390/ma14175100 - 6 Sep 2021

Cited by 5 | Viewed by 1795

Abstract

The properties of the MoS₂/Zr coatings can be significantly affected by the deposition temperature. In this study, the MoS₂/Zr composite coatings were fabricated on the cemented carbide surface, utilizing the duplex deposition technology at various deposition temperatures. The effects [...] Read more.

The properties of the MoS₂/Zr coatings can be significantly affected by the deposition temperature. In this study, the MoS₂/Zr composite coatings were fabricated on the cemented carbide surface, utilizing the duplex deposition technology at various deposition temperatures. The effects of deposition temperature on the mechanical and friction properties of the MoS₂/Zr coatings were systematically studied. Results exhibited that as the deposition temperature increased, the adhesion force increased first and then decreased, and the coating thickness and micro-hardness gradually increased. Dry sliding tests against a hardened steel ring showed that the tribological behaviors and wear mechanisms of the MoS₂/Zr coatings varied with deposition temperature, which were due to the changing mechanical properties of coatings caused by the temperature. The coatings deposited at a temperature of 180 °C and 200 °C possessed preferable comprehensive mechanical and tribological properties. Full article

(This article belongs to the Special Issue Fabrication, Characterization, and Application of Coatings and Thin Films)

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21 pages, 4924 KiB

Open AccessArticle

Experimental and Analytical Analysis of Mechanical Properties for Large-Size Lattice Truss Panel Structure Including Role of Connected Structure

by Shaohua Li, Wenchun Jiang, Xiaolei Zhu and Xuefang Xie

Materials 2021, 14(17), 5099; https://doi.org/10.3390/ma14175099 - 6 Sep 2021

Cited by 2 | Viewed by 1973

Abstract

The large-size lattice truss panel structure (LTPS) is continually increasing for higher upsizing, but the roles of its connected structures on the mechanical properties are always ignored during the previous structural integrity assessment. Thus, in this paper, a series of mechanical tests, including [...] Read more.

The large-size lattice truss panel structure (LTPS) is continually increasing for higher upsizing, but the roles of its connected structures on the mechanical properties are always ignored during the previous structural integrity assessment. Thus, in this paper, a series of mechanical tests, including the fabricating of panel-to-panel LTPSs, monotonous tensile, and three- and four-point bending tests, were performed to comprehensively understand the mechanical behavior. Furthermore, a theoretical model including the role of connected structures was developed to predict both the elastic and plastic deformation behavior of panel-to-panel LTPS. Results show that the connected structure has a very significant effect on the mechanical properties of panel-to-panel LTPS during the three-bending tests, and I-beam element depresses its carrying capacity. The developed theoretical model was proved to accurately predict the experimental results, and the maximum error was limited within 20%. Finally, the dimensional effects of the connection components on mechanical properties were also analyzed by the theoretical model, and indicated that the panel-to-panel LTPS will present better mechanical performance than the intact structure when the width of I-beam element exceeds 12.2 mm or the its length downgrades to 39.1 mm, which provide a comprehensive guidance for the engineering design of large-size LTPS. Full article

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21 pages, 7107 KiB

Open AccessArticle

Optimizing the Mechanical Properties of Ultra-High-Performance Fibre-Reinforced Concrete to Increase Its Resistance to Projectile Impact

by Anna L. Mina, Konstantinos G. Trezos and Michael F. Petrou

Materials 2021, 14(17), 5098; https://doi.org/10.3390/ma14175098 - 6 Sep 2021

Cited by 10 | Viewed by 3449

Abstract

This study describes an extensive experimental investigation of various mechanical properties of Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC). The scope is to achieve high strength and ductile behaviour, hence providing optimal resistance to projectile impact. Eight different mixtures were produced and tested, three mixtures of [...] Read more.

This study describes an extensive experimental investigation of various mechanical properties of Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC). The scope is to achieve high strength and ductile behaviour, hence providing optimal resistance to projectile impact. Eight different mixtures were produced and tested, three mixtures of Ultra-High-Performance Concrete (UHPC) and five mixtures of UHPFRC, by changing the amount and length of the steel fibres, the quantity of the superplasticizer, and the water to binder (w/b) ratio. Full stress–strain curves from compression, direct tension, and flexural tests were obtained from one batch of each mixture to examine the influence of the above parameters on the mechanical properties. The Poisson’s ratio and modulus of elasticity in compression and direct tension were measured. Additionally, a factor was determined to convert the cubic strength to cylindrical. Based on the test results, the mixture with high volume (6%) and a combination of two lengths of steel fibres (3% each), water to binder ratio of 0.16% and 6.1% of superplasticizer to binder ratio exhibited the highest strength and presented great deformability in the plastic region. A numerical simulation developed using ABAQUS was capable of capturing very well the experimental three-point bending response of the UHPFRC best-performed mixture. Full article

(This article belongs to the Special Issue Research of Mechanical Behavior of Cement and Concrete Composites)

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21 pages, 4675 KiB

Open AccessReview

Microwave Measurements of Electromagnetic Properties of Materials

by Jerzy Krupka

Materials 2021, 14(17), 5097; https://doi.org/10.3390/ma14175097 - 6 Sep 2021

Cited by 24 | Viewed by 4218

Abstract

A review of measurement methods of the basic electromagnetic parameters of materials at microwave frequencies is presented. Materials under study include dielectrics, semiconductors, conductors, superconductors, and ferrites. Measurement methods of the complex permittivity, the complex permeability tensor, and the complex conductivity and related [...] Read more.

A review of measurement methods of the basic electromagnetic parameters of materials at microwave frequencies is presented. Materials under study include dielectrics, semiconductors, conductors, superconductors, and ferrites. Measurement methods of the complex permittivity, the complex permeability tensor, and the complex conductivity and related parameters, such as resistivity, the sheet resistance, and the ferromagnetic linewidth are considered. For dielectrics and ferrites, the knowledge of their complex permittivity and the complex permeability at microwave frequencies is of practical interest. Microwave measurements allow contactless measurements of their resistivity, conductivity, and sheet resistance. These days contactless conductivity measurements have become more and more important, due to the progress in materials technology and the development of new materials intended for the electronic industry such as graphene, GaN, and SiC. Some of these materials, such as GaN and SiC are not measurable with the four-point probe technique, even if they are conducting. Measurement fixtures that are described in this paper include sections of transmission lines, resonance cavities, and dielectric resonators. Full article

(This article belongs to the Special Issue Advanced Techniques for Materials Characterization)

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37 pages, 38226 KiB

Open AccessArticle

Suppression of the High-Frequency Errors in Surface Topography Measurements Based on Comparison of Various Spline Filtering Methods

by Przemysław Podulka

Materials 2021, 14(17), 5096; https://doi.org/10.3390/ma14175096 - 6 Sep 2021

Cited by 23 | Viewed by 2874

Abstract

The metrology of so-called “engineering surfaces” is burdened with a substantial risk of both measurement and data analysis errors. One of the most encouraging issues is the definition of frequency-defined measurement errors. This paper proposes a new method for the suppression and reduction [...] Read more.

The metrology of so-called “engineering surfaces” is burdened with a substantial risk of both measurement and data analysis errors. One of the most encouraging issues is the definition of frequency-defined measurement errors. This paper proposes a new method for the suppression and reduction of high-frequency measurement errors from the surface topography data. This technique is based on comparisons of alternative types of noise detection procedures with the examination of profile (2D) or surface (3D) details for both measured and modelled surface topography data. In this paper, the results of applying various spline filters used for suppressions of measurement noise were compared with regard to several kinds of surface textures. For the purpose of the article, the influence of proposed approaches on the values of surface topography parameters (from ISO 25178 for areal and ISO 4287 for profile standards) was also performed. The effect of the distribution of some features of surface texture on the results of suppressions of high-frequency measurement noise was also closely studied. Therefore, the surface topography analysis with Power Spectral Density, Autocorrelation Function, and novel approaches based on the spline modifications or studies of the shape of an Autocorrelation Function was presented. Full article

(This article belongs to the Special Issue Machining and Surface Properties of Steel Parts)

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17 pages, 12640 KiB

Open AccessArticle

Image Processing of Mg-Al-Sn Alloy Microstructures for Determining Phase Ratios and Grain Size and Correction with Manual Measurement

by Ali Ercetin, Fatih Akkoyun, Ercan Şimşir, Danil Yurievich Pimenov, Khaled Giasin, Manjunath Patel Gowdru Chandrashekarappa, Avinash Lakshmikanthan and Szymon Wojciechowski

Materials 2021, 14(17), 5095; https://doi.org/10.3390/ma14175095 - 6 Sep 2021

Cited by 21 | Viewed by 3456

Abstract

The study of microstructures for the accurate control of material properties is of industrial relevance. Identification and characterization of microstructural properties by manual measurement are often slow, labour intensive, and have a lack of repeatability. In the present work, the intermetallic phase ratio [...] Read more.

The study of microstructures for the accurate control of material properties is of industrial relevance. Identification and characterization of microstructural properties by manual measurement are often slow, labour intensive, and have a lack of repeatability. In the present work, the intermetallic phase ratio and grain size in the microstructure of known Mg-Sn-Al alloys were measured by computer vision (CV) technology. New Mg (Magnesium) alloys with different alloying element contents were selected as the work materials. Mg alloys (Mg-Al-Sn) were produced using the hot-pressing powder metallurgy technique. The alloys were sintered at 620 °C under 50 MPa pressure in an argon gas atmosphere. Scanning electron microscopy (SEM) images were taken for all the fabricated alloys (three alloys: Mg-7Al-5Sn, Mg-8Al-5Sn, Mg-9Al-5Sn). From the SEM images, the grain size was counted manually and automatically with the application of CV technology. The obtained results were evaluated by correcting automated grain counting procedures with manual measurements. The accuracy of the automated counting technique for determining the grain count exceeded 92% compared to the manual counting procedure. In addition, ASTM (American Society for Testing and Materials) grain sizes were accurately calculated (approximately 99% accuracy) according to the determined grain counts in the SEM images. Hence, a successful approach was proposed by calculating the ASTM grain sizes of each alloy with respect to manual and automated counting methods. The intermetallic phases (Mg₁₇Al₁₂ and Mg₂Sn) were also detected by theoretical calculations and automated measurements. The accuracy of automated measurements for Mg₁₇Al₁₂ and Mg₂Sn intermetallic phases were over 95% and 97%, respectively. The proposed automatic image processing technique can be used as a tool to track and analyse the grain and intermetallic phases of the microstructure of other alloys such as AZ31 and AZ91 magnesium alloys, aluminium, titanium, and Co alloys. Full article

(This article belongs to the Special Issue Artificial Intelligence for Advanced Materials Research)

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30 pages, 3218 KiB

Open AccessReview

Sustainable Hydrothermal and Solvothermal Synthesis of Advanced Carbon Materials in Multidimensional Applications: A Review

by Lwazi Ndlwana, Naledi Raleie, Kgogobi M. Dimpe, Hezron F. Ogutu, Ekemena O. Oseghe, Mxolisi M. Motsa, Titus A.M. Msagati and Bhekie B. Mamba

Materials 2021, 14(17), 5094; https://doi.org/10.3390/ma14175094 - 6 Sep 2021

Cited by 72 | Viewed by 9766

Abstract

The adoption of green technology is very important to protect the environment and thus there is a need for improving the existing methods for the fabrication of carbon materials. As such, this work proposes to discuss, interrogate, and propose viable hydrothermal, solvothermal, and [...] Read more.

The adoption of green technology is very important to protect the environment and thus there is a need for improving the existing methods for the fabrication of carbon materials. As such, this work proposes to discuss, interrogate, and propose viable hydrothermal, solvothermal, and other advanced carbon materials synthesis methods. The synthesis approaches for advanced carbon materials to be interrogated will include the synthesis of carbon dots, carbon nanotubes, nitrogen/titania-doped carbons, graphene quantum dots, and their nanocomposites with solid/polymeric/metal oxide supports. This will be performed with a particular focus on microwave-assisted solvothermal and hydrothermal synthesis due to their favourable properties such as rapidity, low cost, and being green/environmentally friendly. These methods are regarded as important for the current and future synthesis and modification of advanced carbon materials for application in energy, gas separation, sensing, and water treatment. Simultaneously, the work will take cognisance of methods reducing the fabrication costs and environmental impact while enhancing the properties as a direct result of the synthesis methods. As a direct result, the expectation is to impart a significant contribution to the scientific body of work regarding the improvement of the said fabrication methods. Full article

(This article belongs to the Special Issue Carbon Nanostructures: Synthesis, Characterization, Properties, and Applications)

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13 pages, 1841 KiB

Open AccessArticle

Influence of Spin Coating Parameters on Gas Transport Properties of Thin-Film Composite Membranes

by Stepan Sokolov, Alexey Balynin, Danila Bakhtin and Ilya Borisov

Materials 2021, 14(17), 5093; https://doi.org/10.3390/ma14175093 - 6 Sep 2021

Cited by 2 | Viewed by 2416

Abstract

The influence of casting centrifugation process parameters, such as a rotation speed (ω), the amount of the film-forming solution (V), and its concentration (C) on transport properties of composite membranes were investigated. A number of composite membranes based on poly (1-trimethylsilylpropyne) (PTMSP) and [...] Read more.

The influence of casting centrifugation process parameters, such as a rotation speed (ω), the amount of the film-forming solution (V), and its concentration (C) on transport properties of composite membranes were investigated. A number of composite membranes based on poly (1-trimethylsilylpropyne) (PTMSP) and micro- (MFFK-1) and ultrafiltration (UFFK) membranes were obtained using the spin-coating method. For the first time, an unexpected dependence of permeance and ideal selectivity on rotation speed had been discovered: the thickness of the selective layer decreases from 3.0 to 1.0 μm for MFFK-1 and from 1.7 to 1.1 μm for UFFK with an increase of spin coater rotation speed from 500 to 3000 rpm. However, the gas permeance of composite membranes in the range of 500–2000 rpm was reduced due to an increase of a penetration depth of PTMSP into a support layer porous structure (estimated by the EDX method). The permeance of the PTMSP/UFFK membranes was higher than PTMSP/MFFK-1 membranes due to a thinner selective layer and a lower penetration depth of polymer solution into the pores of the support. The highest CO₂/N₂ selectivity values were achieved as 5.65 ± 0.9 at CO₂ permeance 5600 ± 1000 GPU for PTMSP/UFFK membranes (C_PTMSP = 0.35%, V_solution = 1 mL, ω = 1000 rpm), and 6.1 ± 0.5 at CO₂ permeance 4090 ± 500 GPU for PTMSP/MFFK-1 membranes (C_PTMSP = 0.35%, V_solution = 1 mL, ω = 2000 rpm). Full article

(This article belongs to the Special Issue Advanced Modification of Membrane Materials)

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15 pages, 14310 KiB

Open AccessArticle

Push-Out Method for Micro Measurements of Interfacial Strength in Aluminium Alloy Matrix Composites

by Rafał Kozera, Anna Boczkowska, Zuzanna D. Krawczyk, Paulina Kozera, Maciej Spychalski, Marcin Malek and Robert Kosturek

Materials 2021, 14(17), 5092; https://doi.org/10.3390/ma14175092 - 6 Sep 2021

Cited by 1 | Viewed by 2407

Abstract

The main goal of this work was the evaluation of the interfacial strength of the carbon fibres/aluminium matrix interface dependently on the utilised composite fabrication method, namely high pressure die casting and gas pressure infiltration. In addition, the influence of a Ni-P coating [...] Read more.

The main goal of this work was the evaluation of the interfacial strength of the carbon fibres/aluminium matrix interface dependently on the utilised composite fabrication method, namely high pressure die casting and gas pressure infiltration. In addition, the influence of a Ni-P coating on the C-fibres was investigated. The proposed measurements of the interfacial strength were carried out by means of the “push-out” method. The interfacial strength of the samples fabricated using the high-pressure infiltration method average between 19.03 MPa and 45.34 MPa. Full article

(This article belongs to the Topic Metallurgical and Materials Engineering)

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16 pages, 4306 KiB

Open AccessArticle

Rheological Performance of Magnetorheological Grease with Embedded Graphite Additives

by Nur Alyaa Mohd Nasir, Nurhazimah Nazmi, Norzilawati Mohamad, Ubaidillah Ubaidillah, Nur Azmah Nordin, Saiful Amri Mazlan, Siti Aishah Abdul Aziz, Muhammad Kashfi Shabdin and Nurul Azhani Yunus

Materials 2021, 14(17), 5091; https://doi.org/10.3390/ma14175091 - 6 Sep 2021

Cited by 19 | Viewed by 2674

Abstract

The use of highly viscous grease as a medium in magnetorheological grease (MRG) provides the benefit of avoiding sedimentation from occurring. However, it limits the expansion of yield stress in the on-state condition, thus reducing the application performance during operation. Therefore, in this [...] Read more.

The use of highly viscous grease as a medium in magnetorheological grease (MRG) provides the benefit of avoiding sedimentation from occurring. However, it limits the expansion of yield stress in the on-state condition, thus reducing the application performance during operation. Therefore, in this study, the improvement in the rheological properties of MRG was investigated through the introduction of graphite as an additive. MRG with 10 wt % graphite (GMRG) was fabricated, and its properties were compared to a reference MRG sample. The microstructure of GMRG was characterized using an environmental scanning electron microscope (ESEM). The rheological properties of both samples, including apparent viscosity, yield stress, and viscoelasticity, were examined using a shear rheometer in rotational and oscillatory modes. The results demonstrated a slight increase in the apparent viscosity in GMRG and a significant improvement in yield stress by 38.8% at 3 A with growth about 32.7% higher compared to MRG from 0 to 3 A. An expansion of the linear viscoelastic region (LVE) from 0.01% to 0.1% was observed for the GMRG, credited to the domination of the elastic properties on the sample. These obtained results were confirmed based on ESEM, which described the contribution of graphite to constructing a more stable chain structure in the GMRG. In conclusion, the findings highlight the influence of the addition of graphite on improving the rheological properties of MRG. Hence, the addition of graphite in MRG shows the potential to be applied in many applications in the near future. Full article

(This article belongs to the Special Issue Nanofabrication, Characterization and Application of Magnetic Functional Materials)

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15 pages, 4851 KiB

Open AccessArticle

Determination of the Influence of Hydraulic Additives on the Foaming Process and Stability of the Produced Geopolymer Foams

by Michał Łach, Kinga Pławecka, Agnieszka Bąk, Katarzyna Lichocka, Kinga Korniejenko, An Cheng and Wei-Ting Lin

Materials 2021, 14(17), 5090; https://doi.org/10.3390/ma14175090 - 6 Sep 2021

Cited by 23 | Viewed by 2842

Abstract

The research described in this article was aimed at determining the influence of hydraulic additives on the foaming process and the stability of the produced geopolymer foams. These foams can be used as insulation materials to replace the currently commonly used insulations such [...] Read more.

The research described in this article was aimed at determining the influence of hydraulic additives on the foaming process and the stability of the produced geopolymer foams. These foams can be used as insulation materials to replace the currently commonly used insulations such as expanded polystyrene or polyurethane foams. Geopolymers have low thermal conductivity, excellent fire- and heat-resistant properties, and have fairly good mechanical properties. Research on foamed materials shows that they have the highest class of fire resistance; therefore, they are most often used as insulation products in construction. Geopolymer foams were made of aluminosilicate materials (fly ash) and foaming agents (H₂O₂ and Al powder), and the stabilizers were gypsum and portland cement. Additionally, surfactants were also used. It was found that better foaming effects were obtained for H₂O₂—it is a better foaming agent for geopolymers than Al powder. When using a hydraulic additive—a stabilizer in the form of cement—lower densities and better insulation parameters were obtained than when using gypsum. Portland cement is a better stabilizer than gypsum (calcium sulfates), although the effect may change due to the addition of surfactants, for example. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications)

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21 pages, 7536 KiB

Open AccessArticle

Toughness Behavior of SBR Acrylate Copolymer-Modified Pervious Concrete with Single-Sized Aggregates

by Chaohua Zhao, Hualin Li, Yi Peng, Xiaoyao Jia and Ali Rahman

Materials 2021, 14(17), 5089; https://doi.org/10.3390/ma14175089 - 6 Sep 2021

Cited by 7 | Viewed by 2311

Abstract

Pervious concrete is an eco-efficient concrete but has problems regarding its mechanical performance and permeability balance. This research investigated the feasibility of using a combination of styrene–butadiene rubber (SBR) and acrylate polymer to improve the toughness of pervious concrete while keeping its permeability. [...] Read more.

Pervious concrete is an eco-efficient concrete but has problems regarding its mechanical performance and permeability balance. This research investigated the feasibility of using a combination of styrene–butadiene rubber (SBR) and acrylate polymer to improve the toughness of pervious concrete while keeping its permeability. Single-sized aggregate and no sand were considered in the concrete mixture. Acrylate polymers with different solid content, PH, density, and viscosity were emulsion copolymerized with an SBR polymer. Eleven scenarios with different mix proportions and 220 specimens for compressive strength, flexural strength, flexural stiffness, impact resistance, and fracture toughness tests were selected to evaluate the effects of the copolymer on the toughness of copolymer-modified pervious concrete (CMPC). The studies showed that (1) the influence trend of the copolymers generally varied according to different mechanical indexes; (2) XG–6001 acrylate polymer mainly and comprehensively enhanced the toughness of the CMPC; (3) it was difficult to increase the enhancing property of the XG–6001 acrylate polymer with the growth of its mix proportion; (4) the zero-sand pervious concrete with 90% SBR and 10% XG–6001 acrylate emulsion copolymerization proved to have relatively high toughness. The proposed CMPC holds promising application value in sustainability traffic road construction. Full article

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