Materials

17 pages, 4292 KiB

Open AccessArticle

Particle Characteristics’ Influence on FLASH Sintering of Potassium Sodium Niobate: A Relationship with Conduction Mechanisms

by Ricardo Serrazina, Camila Ribeiro, Maria Elisabete Costa, Luis Pereira, Paula M. Vilarinho and Ana M. O. R. Senos

Materials 2021, 14(5), 1321; https://doi.org/10.3390/ma14051321 - 9 Mar 2021

Cited by 10 | Viewed by 3280

Abstract

The considerable decrease in temperature and time makes FLASH sintering a more sustainable alternative for materials processing. FLASH also becomes relevant if volatile elements are part of the material to be processed, as in alkali-based piezoelectrics like the promising lead-free K_0.5Na [...] Read more.

The considerable decrease in temperature and time makes FLASH sintering a more sustainable alternative for materials processing. FLASH also becomes relevant if volatile elements are part of the material to be processed, as in alkali-based piezoelectrics like the promising lead-free K_0.5Na_0.5NbO₃ (KNN). Due to the volatile nature of K and Na, KNN is difficult to process by conventional sintering. Although some studies have been undertaken, much remains to be understood to properly engineer the FLASH sintering process of KNN. In this work, the effect of FLASH temperature, T_F, is studied as a function of the particle size and impurity content of KNN powders. Differences are demonstrated: while the particle size and impurity degree markedly influence T_F, they do not significantly affect the densification and grain growth processes. The conductivity of KNN FLASH-sintered ceramics and KNN single crystals (SCs) is compared to elucidate the role of particles’ surface conduction. When particles’ surfaces are not present, as in the case of SCs, the FLASH process requires higher temperatures and conductivity values. These results have implications in understanding FLASH sintering towards a more sustainable processing of lead-free piezoelectrics. Full article

(This article belongs to the Special Issue Materials Sintering)

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23 pages, 28852 KiB

Open AccessArticle

Influence of Modified Epoxy Resins on Peroxide Curing, Mechanical Properties and Adhesion of SBR, NBR and XNBR to Silver Wires. Part I: Application of Monoperoxy Derivative of Epoxy Resin (PO)

by Joanna Chudzik, Dariusz M. Bieliński, Michael Bratychak, Yuriy Demchuk, Olena Astakhova, Marcin Jędrzejczyk and Grzegorz Celichowski

Materials 2021, 14(5), 1320; https://doi.org/10.3390/ma14051320 - 9 Mar 2021

Cited by 10 | Viewed by 3455

Abstract

The research was aimed at checking the effect of monoperoxy derivative of epoxy resin (PO) on the possibility of rubber crosslinking and a subsequent adhesion of the modified rubber to silver wires. Three of the commonly industrially used rubbers were selected for the [...] Read more.

The research was aimed at checking the effect of monoperoxy derivative of epoxy resin (PO) on the possibility of rubber crosslinking and a subsequent adhesion of the modified rubber to silver wires. Three of the commonly industrially used rubbers were selected for the study: styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR) and carboxylated acrylonitrile-butadiene rubber (XNBR), together with the popular, commercially available Epidian 6 epoxy resin, subjected to the functionalization. An improvement in the adhesion of rubbers to silver wires was observed when using the modified resin. In some cases, an improvement in the mechanical properties of the rubber was observed, especially when the resin was used for crosslinking together with dicumyl peroxide (DCP). Crosslinking synergy between dicumyl peroxide and the modified resin could be observed especially in the case of PO applied for peroxide curing of SBR and NBR. Full article

(This article belongs to the Special Issue Structure–Physical Properties Relationship of Polymer and its Composites)

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11 pages, 2776 KiB

Open AccessEditor’s ChoiceArticle

Chemical Modification of B₄C Films and B₄C/Pd Layers Stored in Different Environments

by Yufei Feng, Runze Qi, Li Jiang, Qiushi Huang, Tongzhou Li, Genchang Liu, Wenbin Li, Wensheng Yan, Zhong Zhang and Zhanshan Wang

Materials 2021, 14(5), 1319; https://doi.org/10.3390/ma14051319 - 9 Mar 2021

Cited by 23 | Viewed by 3115

Abstract

B₄C/Pd multilayers with small d-spacing can easily degrade in the air, and the exact degradation process is not clear. In this work, we studied the chemical modification of B₄C films and B₄C/Pd double layers stored in four [...] Read more.

B₄C/Pd multilayers with small d-spacing can easily degrade in the air, and the exact degradation process is not clear. In this work, we studied the chemical modification of B₄C films and B₄C/Pd double layers stored in four different environments: a dry nitrogen environment, the atmosphere, a dry oxygen-rich environment, and a wet nitrogen environment. The XANES spectra of the B₄C/Pd layers placed in a dry oxygen-rich environment showed the most significant decrease in the σ* states of the B–C bonds and an increase in the π* states of the B–O bonds compared with the other samples. X-ray photoelectron spectroscopy (XPS) measurements of the samples placed in a dry oxygen-rich environment showed more intensive B-O binding signals in the B₄C/Pd layers than in the single B₄C film. The results of the Fourier-transform infrared spectroscopy (FTIR) showed a similar decrease in the B–C bonds and an increase in the B–O bonds in the B₄C/Pd layers in contrast to the single B₄C film placed in a dry oxygen-rich environment. We concluded that the combination of palladium catalysis and the high content of oxygen in the environment promoted the oxidization of boron, deteriorated the B₄C composition. Full article

(This article belongs to the Section Materials Physics)

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22 pages, 2954 KiB

Open AccessEditor’s ChoiceReview

Applications of Additively Manufactured Tools in Abrasive Machining—A Literature Review

by Mariusz Deja, Dawid Zieliński, Aini Zuhra Abdul Kadir and Siti Nur Humaira

Materials 2021, 14(5), 1318; https://doi.org/10.3390/ma14051318 - 9 Mar 2021

Cited by 37 | Viewed by 5758

Abstract

High requirements imposed by the competitive industrial environment determine the development directions of applied manufacturing methods. 3D printing technology, also known as additive manufacturing (AM), currently being one of the most dynamically developing production methods, is increasingly used in many different areas of [...] Read more.

High requirements imposed by the competitive industrial environment determine the development directions of applied manufacturing methods. 3D printing technology, also known as additive manufacturing (AM), currently being one of the most dynamically developing production methods, is increasingly used in many different areas of industry. Nowadays, apart from the possibility of making prototypes of future products, AM is also used to produce fully functional machine parts, which is known as Rapid Manufacturing and also Rapid Tooling. Rapid Manufacturing refers to the ability of the software automation to rapidly accelerate the manufacturing process, while Rapid Tooling means that a tool is involved in order to accelerate the process. Abrasive processes are widely used in many industries, especially for machining hard and brittle materials such as advanced ceramics. This paper presents a review on advances and trends in contemporary abrasive machining related to the application of innovative 3D printed abrasive tools. Examples of abrasive tools made with the use of currently leading AM methods and their impact on the obtained machining results were indicated. The analyzed research works indicate the great potential and usefulness of the new constructions of the abrasive tools made by incremental technologies. Furthermore, the potential and limitations of currently used 3D printed abrasive tools, as well as the directions of their further development are indicated. Full article

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

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13 pages, 2514 KiB

Open AccessArticle

Influence of Relative Displacement on Surface Roughness in Longitudinal Turning of X37CrMoV5-1 Steel

by Michal Skrzyniarz, Lukasz Nowakowski, Edward Miko and Krzysztof Borkowski

Materials 2021, 14(5), 1317; https://doi.org/10.3390/ma14051317 - 9 Mar 2021

Cited by 15 | Viewed by 2496

Abstract

The shaping process of surface texture is complicated and depends on many factors and phenomena accompanying them. This article presents the author’s test stand for the measurement of relative displacements in a tool–workpiece system during longitudinal turning. The aim of this study was [...] Read more.

The shaping process of surface texture is complicated and depends on many factors and phenomena accompanying them. This article presents the author’s test stand for the measurement of relative displacements in a tool–workpiece system during longitudinal turning. The aim of this study was to determine the influence of edge radius on the relative displacement between the tool and workpiece. The cutting process was carried out with inserts with different edge radii for X37CrMoV5-1 steel. As a result of the research, vibration charts of the tool–workpiece system were obtained. In the range of feed 0.03–0.18 mm/rev, the values of the standard deviation of relative displacements in the x-axis were obtained in the range of 0.36–0.78 μm for the insert with an edge radius of r_n = 48.8 μm. As a result of the work, it was determined that for the feed value of 0.12 mm/rev for all inserts, the relative displacements are the smallest. As the final effect, the formula for forecasting the Ra roughness parameter was presented. Full article

(This article belongs to the Section Materials Simulation and Design)

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14 pages, 4209 KiB

Open AccessArticle

Opuntia Ficus-Indica (OFI) Mucilage as Corrosion Inhibitor of Steel in CO₂-Contaminated Mortar

by Andrés A. Torres-Acosta and Paola Y. González-Calderón

Materials 2021, 14(5), 1316; https://doi.org/10.3390/ma14051316 - 9 Mar 2021

Cited by 16 | Viewed by 2814

Abstract

The present investigation is directed to determine if a natural/botanical addition, from Opuntia ficus-indica (OFI) cactus, increases durability for cement-based materials exposed to CO₂-laden environments (urban and industrial). The use of this botanical addition in cement-based material applications has shown good [...] Read more.

The present investigation is directed to determine if a natural/botanical addition, from Opuntia ficus-indica (OFI) cactus, increases durability for cement-based materials exposed to CO₂-laden environments (urban and industrial). The use of this botanical addition in cement-based material applications has shown good performance when these materials are exposed to chloride-laden environments, but no investigations to date have shown the performance of this addition in urban/industrial environments. Therefore, the aim of this investigation is to complement OFI mucilage performance in the most hazardous environments where most of these construction materials are naturally exposed: marine, urban, and industrial. Steel-reinforced mortar prisms, containing OFI mucilage at different addition levels (0%, 1.5%, 4%, 8%, 42%, and 95%, by water mass replacement concentration), were exposed for 14 years (5110 days) in a natural CO₂-laden environment. Linear polarization resistance measurements were performed in a wet–dry cycle (between 5020 and 5110 days of age, after mortar fabrication) to determine the possible corrosion-inhibiting effect of OFI mucilage additions. Little corrosion-induced cracking was observed in carbonated mortars with OFI mucilage additions, compared with the carbonated control mortar that showed high corrosion-induced cracking. The electrochemical results showed corrosion-inhibiting efficiencies for steel in carbonated mortar with OFI mucilage additions of 40–70% for low OFI mucilage concentrations (1.5% and 4%), and 70–90% for medium and high OFI mucilage concentrations (8%, 42%, and 95%). Experimental findings suggest that adding OFI mucilage might be useful as a corrosion inhibitor for steel in carbonated cement-based materials (i.e., mortar) because corrosion rates and cracking initiation/propagation were decreased. Full article

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

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12 pages, 10719 KiB

Open AccessArticle

The Influence of Structure of Multilayer Woven Fabrics on Their Mechanical Properties

by Ewa Witczak, Izabela Jasińska and Iwona Krawczyńska

Materials 2021, 14(5), 1315; https://doi.org/10.3390/ma14051315 - 9 Mar 2021

Cited by 7 | Viewed by 2589

Abstract

Multilayer woven fabrics used for conveyor belts must be characterized by high mechanical strength. The design process of multilayer woven fabrics for such application requires taking into account the structural characteristics of the fabric, which allows to adjust the final product properties to [...] Read more.

Multilayer woven fabrics used for conveyor belts must be characterized by high mechanical strength. The design process of multilayer woven fabrics for such application requires taking into account the structural characteristics of the fabric, which allows to adjust the final product properties to the dedicated use. The geometry of warp threads—means stuffer and binding is the decisive aspect, which influences the strength properties of multilayer woven fabrics and materials made with their use as well. The aim of this work was to examine the possibility of shaping mechanical strength and bending rigidity of multilayer woven fabrics by changing the order of introducing weft threads into individual layers. The eight variants of multilayer woven fabrics were manufactured using laboratory harness loom. They were produced using different structural models in two weft variants, then tested. The mechanical features were determined, such as breaking force, recovered and unrecovered elongations in cyclic tensile test, stiffness rigidity. The analysis of the obtained results confirmed, that both the model and the order in which the weft threads were introduced into individual layers influence the mechanical strength and bending rigidity of multilayer woven. It was found, that the strength properties characterized by the above mentioned indicators are influenced by the number of threads weaved as both the stuffer and binding warp. Full article

(This article belongs to the Section Advanced Materials Characterization)

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14 pages, 701 KiB

Open AccessArticle

Exploiting the Acceleration Voltage Dependence of EMCD

by Stefan Löffler, Michael Stöger-Pollach, Andreas Steiger-Thirsfeld, Walid Hetaba and Peter Schattschneider

Materials 2021, 14(5), 1314; https://doi.org/10.3390/ma14051314 - 9 Mar 2021

Cited by 2 | Viewed by 2478

Abstract

Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for measuring magnetism down to the atomic scale in transmission electron microscopy (TEM). As the magnetic signal is encoded in the phase of the electron wave, any process distorting this characteristic phase is detrimental [...] Read more.

Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for measuring magnetism down to the atomic scale in transmission electron microscopy (TEM). As the magnetic signal is encoded in the phase of the electron wave, any process distorting this characteristic phase is detrimental for EMCD. For example, elastic scattering gives rise to a complex thickness dependence of the signal. Since the details of elastic scattering depend on the electron’s energy, EMCD strongly depends on the acceleration voltage. Here, we quantitatively investigate this dependence in detail, using a combination of theory, numerical simulations, and experimental data. Our formulas enable scientists to optimize the acceleration voltage when performing EMCD experiments. Full article

(This article belongs to the Special Issue Advances in Transmission Electron Microscopy for the Study of Soft and Hard Matter)

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10 pages, 3190 KiB

Open AccessEditor’s ChoiceArticle

Carbon Dot/Naphthalimide Based Ratiometric Fluorescence Biosensor for Hyaluronidase Detection

by Pushap Raj, Seon-yeong Lee and Tae Yoon Lee

Materials 2021, 14(5), 1313; https://doi.org/10.3390/ma14051313 - 9 Mar 2021

Cited by 29 | Viewed by 3708

Abstract

Bladder cancer is the leading cause of death in patients with genitourinary cancer. An elevated level of hyaluronidase (HAase) was found in bladder cancer, which acts as an important biomarker for the early diagnosis of bladder cancer. Hence, there is a need to [...] Read more.

Bladder cancer is the leading cause of death in patients with genitourinary cancer. An elevated level of hyaluronidase (HAase) was found in bladder cancer, which acts as an important biomarker for the early diagnosis of bladder cancer. Hence, there is a need to develop a simple enzymatic assay for the early recognition of HAase. Herein, we report a simple, sensitive, and ratiometric fluorescence assay for HAase detection under physiological conditions. The fluorescence assay was constructed by the adsorption of cationic carbon dots and positively charged naphthalimide on negatively charged hyaluronic acid and the development of a Förster resonance energy transfer (FRET) mechanism from carbon dots to a naphthalimide fluorophores. The hyaluronidase enzyme cleaves the hyaluronic acid in this assay, and breaking down the FRET mechanism induces ratiometric changes. A detection limit of 0.09 U/mL was achieved, which is less than the HAase level found in normal human body fluids. Moreover, this assay may be used for diagnosing HAase-related diseases. Full article

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

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16 pages, 21820 KiB

Open AccessArticle

Adsorptive Removal of Phosphate from Aqueous Solutions Using Low-Cost Volcanic Rocks: Kinetics and Equilibrium Approaches

by Dereje Tadesse Mekonnen, Esayas Alemayehu and Bernd Lennartz

Materials 2021, 14(5), 1312; https://doi.org/10.3390/ma14051312 - 9 Mar 2021

Cited by 26 | Viewed by 4662

Abstract

The contamination of surface and groundwater with phosphate originating from industrial and household wastewater remains a serious environmental issue in low-income countries. Herein, phosphate removal from aqueous solutions was studied using low-cost volcanic rocks such as pumice (VPum) and scoria (VSco), obtained from [...] Read more.

The contamination of surface and groundwater with phosphate originating from industrial and household wastewater remains a serious environmental issue in low-income countries. Herein, phosphate removal from aqueous solutions was studied using low-cost volcanic rocks such as pumice (VPum) and scoria (VSco), obtained from the Ethiopian Great Rift Valley. Batch adsorption experiments were conducted using phosphate solutions with concentrations of 0.5 to 25 mg·L⁻¹ to examine the adsorption kinetic as well as equilibrium conditions. The experimental adsorption data were tested by employing various equilibrium adsorption models, and the Freundlich and Dubinin-Radushkevich (D-R) isotherms best depicted the observations. The maximum phosphate adsorption capacities of VPum and VSco were calculated and found to be 294 mg·kg⁻¹ and 169 mg·kg⁻¹, respectively. A pseudo-second-order kinetic model best described the experimental data with a coefficient of correlation of R² > 0.99 for both VPum and VSco; however, VPum showed a slightly better selectivity for phosphate removal than VSco. The presence of competitive anions markedly reduced the removal efficiency of phosphate from the aqueous solution. The adsorptive removal of phosphate was affected by competitive anions in the order: HCO₃⁻ >F⁻ > SO₄⁻² > NO₃⁻ > Cl⁻ for VPum and HCO₃⁻ > F⁻ > Cl⁻ > SO₄⁻² > NO₃⁻ for VSco. The results indicate that the readily available volcanic rocks have a good adsorptive capacity for phosphate and shall be considered in future studies as test materials for phosphate removal from water in technical-scale experiments. Full article

(This article belongs to the Special Issue Novel Inorganic Adsorbents for Environmental Purification)

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23 pages, 4028 KiB

Open AccessArticle

Laser-Assisted High Speed Machining of 316 Stainless Steel: The Effect of Water-Soluble Sago Starch Based Cutting Fluid on Surface Roughness and Tool Wear

by Farhana Yasmin, Khairul Fikri Tamrin, Nadeem Ahmed Sheikh, Pierre Barroy, Abdullah Yassin, Amir Azam Khan and Shahrol Mohamaddan

Materials 2021, 14(5), 1311; https://doi.org/10.3390/ma14051311 - 9 Mar 2021

Cited by 7 | Viewed by 3161

Abstract

Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material’s surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high [...] Read more.

Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material’s surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high speed leads to high friction between workpiece and tool, and can result in high temperatures, impairing the surface quality. Use of conventional cutting fluid may not effectively control the heat generation. Besides, vegetable-based cutting fluids are invariably a major source of food insecurity of edible oils which is traditionally used as a staple food in many countries. Thus, the primary objective of this study is to experimentally investigate the effects of water-soluble sago starch-based cutting fluid on surface roughness and tool’s flank wear using response surface methodology (RSM) while machining of 316 stainless steel. In order to observe the comparison, the experiments with same machining parameters are conducted with conventional cutting fluid. The prepared water-soluble sago starch based cutting fluid showed excellent cooling and lubricating performance. Therefore, in comparison to the machining using conventional cutting fluid, a decrease of 48.23% in surface roughness and 38.41% in flank wear were noted using presented approach. Furthermore, using the extreme learning machine (ELM), the obtained data is modeled to predict surface roughness and flank wear and showed good agreement between observations and predictions. Full article

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11 pages, 19943 KiB

Open AccessArticle

Comparison of Hook and Straight Steel Fibers Addition on Malaysian Fly Ash-Based Geopolymer Concrete on the Slump, Density, Water Absorption and Mechanical Properties

by Meor Ahmad Faris, Mohd Mustafa Al Bakri Abdullah, Ratnasamy Muniandy, Mohammad Firdaus Abu Hashim, Katarzyna Błoch, Bartłomiej Jeż, Sebastian Garus, Paweł Palutkiewicz, Nurul Aida Mohd Mortar and Mohd Fathullah Ghazali

Materials 2021, 14(5), 1310; https://doi.org/10.3390/ma14051310 - 9 Mar 2021

Cited by 48 | Viewed by 4340

Abstract

Geopolymer concrete has the potential to replace ordinary Portland cement which can reduce carbon dioxide emission to the environment. The addition of different amounts of steel fibers, as well as different types of end-shape fibers, could alter the performance of geopolymer concrete. The [...] Read more.

Geopolymer concrete has the potential to replace ordinary Portland cement which can reduce carbon dioxide emission to the environment. The addition of different amounts of steel fibers, as well as different types of end-shape fibers, could alter the performance of geopolymer concrete. The source of aluminosilicate (fly ash) used in the production of geopolymer concrete may lead to a different result. This study focuses on the comparison between Malaysian fly ash geopolymer concrete with the addition of hooked steel fibers and geopolymer concrete with the addition of straight-end steel fibers to the physical and mechanical properties. Malaysian fly ash was first characterized by X-ray fluorescence (XRF) to identify the chemical composition. The sample of steel fiber reinforced geopolymer concrete was produced by mixing fly ash, alkali activators, aggregates, and specific amounts of hook or straight steel fibers. The steel fibers addition for both types of fibers are 0%, 0.5%, 1.0%, 1.5%, and 2.0% by volume percentage. The samples were cured at room temperature. The physical properties (slump, density, and water absorption) of reinforced geopolymer concrete were studied. Meanwhile, a mechanical performance which is compressive, as well as the flexural strength was studied. The results show that the pattern in physical properties of geopolymer concrete for both types of fibers addition is almost similar where the slump is decreased with density and water absorption is increased with the increasing amount of fibers addition. However, the addition of hook steel fiber to the geopolymer concrete produced a lower slump than the addition of straight steel fibers. Meanwhile, the addition of hook steel fiber to the geopolymer concrete shows a higher density and water absorption compared to the sample with the addition of straight steel fibers. However, the difference is not significant. Besides, samples with the addition of hook steel fibers give better performance for compressive and flexural strength compared to the samples with the addition of straight steel fibers where the highest is at 1.0% of fibers addition. Full article

(This article belongs to the Special Issue Properties of Amorphous Materials and Nanomaterials)

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15 pages, 5686 KiB

Open AccessArticle

Influence of the Compaction Method in the Volumetric Design of Cold Recycled Mixtures with Emulsion

by Guillermo Flores, Juan Gallego, Lucía Miranda and José Ramón Marcobal

Materials 2021, 14(5), 1309; https://doi.org/10.3390/ma14051309 - 9 Mar 2021

Cited by 4 | Viewed by 2515

Abstract

Compaction of cold asphalt mixtures is a subject that has not been thoroughly studied, and, for this reason, requires new efforts from researchers to have a better understanding. Unlike hot mixtures, cold mixtures and mainly recycled mixtures require specific considerations for compaction. There [...] Read more.

Compaction of cold asphalt mixtures is a subject that has not been thoroughly studied, and, for this reason, requires new efforts from researchers to have a better understanding. Unlike hot mixtures, cold mixtures and mainly recycled mixtures require specific considerations for compaction. There is a lack of consensus about the methodology to select the optimum premix water and emulsion contents. In the absence of specific regulations, the use of soil tests or hot mixtures procedures is common. For these reasons, this investigation’s main goal was to evaluate two compaction methods used to design cold recycled mixtures with emulsion: the modified Proctor procedure and the gyratory compaction. It was concluded that both methods could be useful to study compactability since consistent results were obtained by applying the maximum bulk density criterion. However, the higher bulk densities achieved, the smaller specimens used, and the suitability of the gyratory specimens to be later tested for mechanical properties make them preferable to the modified Proctor samples. A new approach has been proposed using iso-density lines on dual-axis premix water content-emulsion content graphs that facilitates the study of the influence on compactability of these two factors combined. These contributions can alleviate the laboratory works during the design of cold recycled asphalt mixtures and contribute to a more in-depth knowledge of the combined effect of premix water and emulsion contents on the compactability of cold recycled mixtures with emulsion. Full article

(This article belongs to the Special Issue Asphalt Mixtures with Reclaimed Asphalt Pavement)

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16 pages, 25325 KiB

Open AccessArticle

High Capacity Nanocomposite Layers Based on Nanoparticles of Carbon Materials and Ruthenium Dioxide for Potassium Sensitive Electrode

by Nikola Lenar, Robert Piech and Beata Paczosa-Bator

Materials 2021, 14(5), 1308; https://doi.org/10.3390/ma14051308 - 9 Mar 2021

Cited by 14 | Viewed by 2468

Abstract

This work presents the new concept of designing ion-selective electrodes based on the use of new composite materials consisting of carbon nanomaterials and ruthenium dioxide. Using two different materials varying in microstructure and properties, we could obtain one material for the mediation layer [...] Read more.

This work presents the new concept of designing ion-selective electrodes based on the use of new composite materials consisting of carbon nanomaterials and ruthenium dioxide. Using two different materials varying in microstructure and properties, we could obtain one material for the mediation layer that adopted features coming of both components. Ruthenium dioxide characterized by high electrical capacity and mixed electronic-ionic transduction and nano-metric carbon materials were reportedly proved to improve the properties of ion-selective electrodes. Initially, only the materials and then the final electrodes were tested in the scope of the presented work, using scanning and transmission electron microscope, contact angle microscope, and various electrochemical techniques, including electrochemical impedance spectroscopy and chronopotentiometry. The obtained results confirmed beneficial influence of the designed nanocomposites on the ion-selective electrodes’ properties. Nanosized structure, high capacity (characterized by the electrical capacitance value from approximately 5.5 mF for GR + RuO₂ and CB + RuO₂, up to 14 mF for NT + RuO₂) and low hydrophilicity (represented by the contact angle from 60° for GR+RuO₂, 80° for CB+RuO₂, and up to 100° for NT + RuO₂) of the mediation layer materials, allowed us to obtain water layer-free potassium-selective electrodes, characterized by rapid and stable potentiometric response in a wide range of concentrations-from 10⁻¹ to 10⁻⁶ M K⁺. Full article

(This article belongs to the Special Issue Electrode Materials: Fabrication, Properties, and Applications)

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13 pages, 25501 KiB

Open AccessCommunication

Lithium Disilicate Ceramic Endocrown Biomechanical Response According to Different Pulp Chamber Extension Angles and Filling Materials

by João Paulo Mendes Tribst, Roberto Lo Giudice, Alison Flavio Campos dos Santos, Alexandre Luiz Souto Borges, Laís Regiane Silva-Concílio, Marina Amaral and Giuseppe Lo Giudice

Materials 2021, 14(5), 1307; https://doi.org/10.3390/ma14051307 - 9 Mar 2021

Cited by 24 | Viewed by 5095

Abstract

The purpose of this study is to evaluate the effect of pulp chamber extension angles and filling material mechanical properties on the biomechanical response of a ceramic endocrown. A 3D model of maxillary molar that underwent endodontically treatment was exported to computer aided [...] Read more.

The purpose of this study is to evaluate the effect of pulp chamber extension angles and filling material mechanical properties on the biomechanical response of a ceramic endocrown. A 3D model of maxillary molar that underwent endodontically treatment was exported to computer aided design software to conduct finite element analysis (FEA). The endocrown model was modified considering different pulp chamber extension angles (right angle; 6°, 12° and 18° of axial divergence). The solids were imported into the computer aided engineering software in Standard for the Exchange of Product Data (STEP) format. Nine different filling materials were simulated to seal the orifice of the root canal system under each endocrown restoration (resin composite, bulk-fill resin composite, alkasite, flowable resin composite, glass ionomer cement, autocured resin-reinforced glass ionomer cement, resin cement, bulk-fill flowable resin composite, zinc oxide cement), totaling 36 models. An axial load (300 N) was applied at the occlusal surface. Results were determined by colorimetric graphs of von-Misses stress (VMS) and Maximum Principal Stress (MPS) on tooth, cement layer, and endocrown restorations. VMS distribution showed a similar pattern between the models, with more stress at the load region for the right-angled endocrowns. The MPS showed that the endocrown intaglio surface and cement layer showed different mechanical responses with different filing materials and pulp chamber angles. The stress peaks plotted in the dispersion plot showed that the filling material stiffness is proportional to the stress magnitude in the endocrown, cement layer and tooth adhesive surface. In addition, the higher the pulp chamber preparation angle, the higher the stress peak in the restoration and tooth, and the lower the stress in the cement layer. Therefore, 6° and 12° pulp chamber angles showed more promising balance between the stresses of the adhesive interface structures. Under the conditions of this study, rigid filling materials were avoided to seal the orifice of root canal system when an endocrown restoration was planned as rehabilitation. In addition, the pulp chamber axial walls were prepared between 6° and 12° of divergence to balance the stress magnitude in the adhesive interface for this treatment modality. Full article

(This article belongs to the Special Issue Dental Materials in Endodontic and Post-endodontic Therapy)

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25 pages, 4755 KiB

Open AccessArticle

Nitrogen Dissolution in Liquid Ga and Fe: Comprehensive Ab Initio Analysis, Relevance for Crystallization of GaN

by Jacek Piechota, Stanislaw Krukowski, Petro Sadovyi, Bohdan Sadovyi, Sylwester Porowski and Izabella Grzegory

Materials 2021, 14(5), 1306; https://doi.org/10.3390/ma14051306 - 9 Mar 2021

Cited by 4 | Viewed by 2589

Abstract

The dissolution of molecular nitrogen in Ga and Fe was investigated by ab initio calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between Ga4s and Ga4p and N2p states [...] Read more.

The dissolution of molecular nitrogen in Ga and Fe was investigated by ab initio calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between Ga4s and Ga4p and N2p states whereas for Fe this is by N2p to Fe4s, Fe4p and Fe3d states. Accordingly, the energy of dissolution of N

_{2}

for arbitrarily chosen starting atomic configurations was 0.535 eV/mol and −0.299 eV/mol for Ga and Fe, respectively. For configurations optimized with molecular dynamics, the difference between the corresponding energy values, 1.107 eV/mol and 0.003 eV/mol, was similarly large. Full thermodynamic analysis of chemical potential was made employing entropy-derived terms in a Debye picture. The entropy-dependent terms were obtained via a normal conditions path to avoid singularity of ideal gas entropy at zero K. Nitrogen solubility as a function of temperature and N

_{2}

pressure was evaluated, being much higher for Fe than for Ga. For

T = 1800

K and

p = 10^{4}

bar, the N concentration in Ga was

3 \times 10^{- 3}

at. fr. whereas for Fe, it was

9 \times 10^{- 2}

at. fr. in very good agreement with experimental data. It indicates that liquid Fe could be a prospective solvent for GaN crystallization from metallic solutions. Full article

(This article belongs to the Section Materials Physics)

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16 pages, 3957 KiB

Open AccessArticle

A Kinetic Model for the Modification of Al₂O₃ Inclusions during Calcium Treatment in High-Carbon Hard Wire Steel

by Zuobing Xi, Changrong Li and Linzhu Wang

Materials 2021, 14(5), 1305; https://doi.org/10.3390/ma14051305 - 9 Mar 2021

Cited by 10 | Viewed by 2511

Abstract

Laboratory-scale experiments for the modification of Al₂O₃ inclusions by calcium treatment in high-carbon hard wire steel were performed and the compositions and morphological evolution of inclusions were studied. The kinetics of the modification of Al₂O₃ inclusions by [...] Read more.

Laboratory-scale experiments for the modification of Al₂O₃ inclusions by calcium treatment in high-carbon hard wire steel were performed and the compositions and morphological evolution of inclusions were studied. The kinetics of the modification of Al₂O₃ inclusions by calcium treatment were studied in high-carbon hard wire steel based on the unreacted shrinking core model, considering the transfer of Ca and Al through the boundary layer and within the product layer, coupled with thermodynamic equilibrium at the interfaces. The diffusion of Al in the inclusion layer was the limiting link in the inclusion modification process. The Ca concentration in molten steel had the greatest influence on the inclusion modification time. The modification time for inclusions tended to be longer in the transformation of higher CaO-containing calcium aluminate. The modification of Al₂O₃ into CA₆ was fastest, while the most time was needed to modify CA into C₁₂A₇. It took about six times time longer at the later stage of inclusion modification than at the early stage. The complete modification time for inclusions increased with the square of their radii. The changes of CaO contents with melting time were estimated based on a kinetic model and was consistent with experimental results. Full article

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14 pages, 5274 KiB

Open AccessArticle

Evaluation on the Microstructure and Durability of High-Strength Concrete Containing Electric Arc Furnace Oxidizing Slag

by Tian-Feng Yuan, Se-Hee Hong, Jin-Seok Choi and Young-Soo Yoon

Materials 2021, 14(5), 1304; https://doi.org/10.3390/ma14051304 - 9 Mar 2021

Cited by 7 | Viewed by 2448

Abstract

The application of electric arc furnace oxidizing slag (EAS) in high strength concrete (HSC) as the cementitious material is investigated in this study. The microstructure and mechanical properties of HSC with four different replacement ratios of EAS were evaluated and HSC with two [...] Read more.

The application of electric arc furnace oxidizing slag (EAS) in high strength concrete (HSC) as the cementitious material is investigated in this study. The microstructure and mechanical properties of HSC with four different replacement ratios of EAS were evaluated and HSC with two replacement ratios of ground granulated blast furnace slag (GBS) was used for performance comparison. The results show that the HSC with EAS replacement ratios smaller than 15% undergo similar hydration processes and result in a similar final product when compared with those of NC-NN. Increases in EAS replacement ratio cause a reduction in Ca(OH)₂ content; this, in turn, leads to an increase in porosity and a reduction in compressive strength. In terms of shrinkage behavior under free conditions, mixtures with increasing replacement ratios of cementitious materials saw increasing shrinkage, with the HSC containing EAS being similar to the other specimens. The mixtures containing EAS saw a quite gradual decrease in their freezing and thawing resistance properties as the number of freeze–thaw cycles they underwent increased. However, the efficacy of HSC with less than 15% of EAS is similar to GBS; hence, EAS could replace cement in concrete for certain applications, which would lead to more environmental benefits. Full article

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

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18 pages, 6026 KiB

Open AccessArticle

Mechanical Properties of the Composite Material consisting of β-TCP and Alginate-Di-Aldehyde-Gelatin Hydrogel and Its Degradation Behavior

by Michael Seidenstuecker, Thomas Schmeichel, Lucas Ritschl, Johannes Vinke, Pia Schilling, Hagen Schmal and Anke Bernstein

Materials 2021, 14(5), 1303; https://doi.org/10.3390/ma14051303 - 9 Mar 2021

Cited by 14 | Viewed by 3298

Abstract

This work aimed to determine the influence of two hydrogels (alginate, alginate-di-aldehyde (ADA)/gelatin) on the mechanical strength of microporous ceramics, which have been loaded with these hydrogels. For this purpose, the compressive strength was determined using a Zwick Z005 universal testing machine. In [...] Read more.

This work aimed to determine the influence of two hydrogels (alginate, alginate-di-aldehyde (ADA)/gelatin) on the mechanical strength of microporous ceramics, which have been loaded with these hydrogels. For this purpose, the compressive strength was determined using a Zwick Z005 universal testing machine. In addition, the degradation behavior according to ISO EN 10993-14 in TRIS buffer pH 5.0 and pH 7.4 over 60 days was determined, and its effects on the compressive strength were investigated. The loading was carried out by means of a flow-chamber. The weight of the samples (manufacturer: Robert Mathys Foundation (RMS) and Curasan) in TRIS solutions pH 5 and pH 7 increased within 4 h (mean 48 ± 32 mg) and then remained constant over the experimental period of 60 days. The determination surface roughness showed a decrease in the value for the ceramics incubated in TRIS compared to the untreated ceramics. In addition, an increase in protein concentration in solution was determined for ADA gelatin-loaded ceramics. The macroporous Curasan ceramic exhibited a maximum failure load of 29 ± 9.0 N, whereas the value for the microporous RMS ceramic was 931 ± 223 N. Filling the RMS ceramic with ADA gelatin increased the maximum failure load to 1114 ± 300 N. The Curasan ceramics were too fragile for loading. The maximum failure load decreased for the RMS ceramics to 686.55 ± 170 N by incubation in TRIS pH 7.4 and 651 ± 287 N at pH 5.0. Full article

(This article belongs to the Section Biomaterials)

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31 pages, 2079 KiB

Open AccessReview

Volcanic Ash as a Sustainable Binder Material: An Extensive Review

by Andrés Játiva, Evelyn Ruales and Miren Etxeberria

Materials 2021, 14(5), 1302; https://doi.org/10.3390/ma14051302 - 8 Mar 2021

Cited by 53 | Viewed by 5928

Abstract

The construction industry is affected by the constant growth in the populations of urban areas. The demand for cement production has an increasing environmental impact, and there are urgent demands for alternative sustainable solutions. Volcanic ash (VA) is an abundant low-cost material that, [...] Read more.

The construction industry is affected by the constant growth in the populations of urban areas. The demand for cement production has an increasing environmental impact, and there are urgent demands for alternative sustainable solutions. Volcanic ash (VA) is an abundant low-cost material that, because of its chemical composition and amorphous atomic structure, has been considered as a suitable material to replace Portland cement clinker for use as a binder in cement production. In the last decade, there has been interest in using alkali-activated VA material as an alternative material to replace ordinary Portland cement. In this way, a valuable product may be derived from a currently under-utilized material. Additionally, alkali-activated VA-based materials may be suitable for building applications because of their good densification behaviour, mechanical properties and low porosity. This article describes the most relevant findings from researchers around the world on the role of the chemical composition and mineral contents of VA on reactivity during the alkali-activation reaction; the effect of synthesis factors, which include the concentration of the alkaline activator, the solution-to-binder ratio and the curing conditions, on the properties of alkali-activated VA-based materials; and the mechanical performance and durability properties of these materials. Full article

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20 pages, 9869 KiB

Open AccessArticle

The Effect of Surface Treatment on Structural Properties of CVD Diamond Layers with Different Grain Sizes Studied by Raman Spectroscopy

by Anna Dychalska, Wojciech Koczorowski, Marek Trzcinski, Lidia Mosińska and Mirosław Szybowicz

Materials 2021, 14(5), 1301; https://doi.org/10.3390/ma14051301 - 8 Mar 2021

Cited by 10 | Viewed by 3347

Abstract

Extensive Raman spectroscopy studies combined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate structural and chemical changes in diamond layers deposited by chemical vapour deposition (CVD) upon post-growth treatment with hydrogen. The aim of this study [...] Read more.

Extensive Raman spectroscopy studies combined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate structural and chemical changes in diamond layers deposited by chemical vapour deposition (CVD) upon post-growth treatment with hydrogen. The aim of this study is to characterize the changes in micro-structural properties of diamond layers with different grain sizes and different contents of sp² carbon phase. Hydrogenation or oxidization of diamond layer surface is often performed to modify its properties; however, it can also strongly affect the surface structure. In this study, the impact of hydrogenation on the structure of diamond layer surface and its chemical composition is investigated. Owing to their polycrystalline nature, the structural properties of CVD diamond layers can strongly differ within the same layer. Therefore, in this project, in order to compare the results before and after hydrogen treatment, the diamond layers are subjected to Raman spectroscopy studies in the vicinity of a T-shape marker fabricated on the surface of each diamond layer studied. Full article

(This article belongs to the Special Issue Carbon or Graphene Based Thin Films: Preparation, Properties, and Applications)

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19 pages, 143404 KiB

Open AccessArticle

Reduced Carbonation, Sulfate and Chloride Ingress Due to the Substitution of Cement by 10% Non-Precalcined Bentonite

by Carmen Andrade, Ana Martínez-Serrano, Miguel Ángel Sanjuán and José Antonio Tenorio Ríos

Materials 2021, 14(5), 1300; https://doi.org/10.3390/ma14051300 - 8 Mar 2021

Cited by 17 | Viewed by 3167

Abstract

The Portland cement industry is presently deemed to account for around 7.4% of the carbon dioxide emitted annually worldwide. Clinker production is being reduced worldwide in response to the need to drastically lower greenhouse gas emissions. The trend began in the nineteen seventies [...] Read more.

The Portland cement industry is presently deemed to account for around 7.4% of the carbon dioxide emitted annually worldwide. Clinker production is being reduced worldwide in response to the need to drastically lower greenhouse gas emissions. The trend began in the nineteen seventies with the advent of mineral additions to replace clinker. Blast furnace slag and fly ash, industrial by-products that were being stockpiled in waste heaps at the time, have not commonly been included in cements. Supply of these additions is no longer guaranteed, however, due to restrained activity in the source industries for the same reasons as in clinker production. The search is consequently on for other additions that may lower pollutant gas emissions without altering cement performance. In this study, bentonite, a very common clay, was used as such an addition directly, with no need for precalcination, a still novel approach that has been scantly explored to date for reinforced structural concrete with structural applications. The results of the mechanical strength and chemical resistance (to sulfates, carbonation and chlorides) tests conducted are promising. The carbonation findings proved to be of particular interest, for that is the area where cement with mineral additions tends to be least effective. In the bentonite-bearing material analysed here, however, carbonation resistance was found to be as low as or lower than that observed in plain Portland cement. Full article

(This article belongs to the Special Issue Supplementary Cementitious Materials in Concrete)

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18 pages, 4324 KiB

Open AccessArticle

Behaviour and Properties of Eco-Cement Pastes Elaborated with Recycled Concrete Powder from Construction and Demolition Wastes

by Laura Caneda-Martínez, Manuel Monasterio, Jaime Moreno-Juez, Sagrario Martínez-Ramírez, Rosario García and Moisés Frías

Materials 2021, 14(5), 1299; https://doi.org/10.3390/ma14051299 - 8 Mar 2021

Cited by 62 | Viewed by 4792

Abstract

This work analyses the influence of fine concrete fractions (<5 mm) of different natures —calcareous (HcG) and siliceous (HsT)—obtained from construction and demolition waste (C&DW) on the behaviour of blended cement pastes with partial replacements between 5 and 10%. The two C&DW fractions [...] Read more.

This work analyses the influence of fine concrete fractions (<5 mm) of different natures —calcareous (HcG) and siliceous (HsT)—obtained from construction and demolition waste (C&DW) on the behaviour of blended cement pastes with partial replacements between 5 and 10%. The two C&DW fractions were characterised by different instrumental techniques. Subsequently, their lime-fixing capacity and the physico-mechanical properties of the blended cement pastes were analysed. Lastly, the environmental benefits of reusing these fine wastes in the manufacture of future eco-efficient cement pastes were examined. The results show that HsT and HcG exhibit weak pozzolanic activity, owing to their low reactive silica and alumina content. Despite this, the new cement pastes meet the physical and mechanical requirements of the existing regulations for common cements. It should be highlighted that the blended cement pastes initially showed a coarser pore network, but then they underwent a refinement process between 2 and 28 days, along with a gain in compressive strength, possibly due to the double pozzolanic and filler effect of the wastes. The environmental viability of the blended cements was evaluated in a Life Cycle Assessment (LCA) concluding that the overall environmental impact could be reduced in the same proportion of the replacement rate. This is in line with the Circular Economy goals and the 2030 Agenda for Sustainable Development. Full article

(This article belongs to the Special Issue Novel and Sustainable Civil Engineering Materials: Eco-Design, Properties and New Processing)

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14 pages, 17755 KiB

Open AccessArticle

Improvement of DC Breakdown Strength of the Epoxy/POSS Nanocomposite by Tailoring Interfacial Electron Trap Characteristics

by Farooq Aslam, Zhen Li, Guanghao Qu, Yang Feng, Shijun Li, Shengtao Li and Hangyin Mao

Materials 2021, 14(5), 1298; https://doi.org/10.3390/ma14051298 - 8 Mar 2021

Cited by 18 | Viewed by 3195

Abstract

To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers [...] Read more.

To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity (E_A) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite. Full article

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19 pages, 7874 KiB

Open AccessReview

A Personal View of Microstructure and Properties of Al Alloys

by John Campbell

Materials 2021, 14(5), 1297; https://doi.org/10.3390/ma14051297 - 8 Mar 2021

Cited by 15 | Viewed by 3007

Abstract

This paper presents a personal view by the author of the role of bifilms in Al alloys. The mantra ‘microstructure determines properties’ is widely accepted as a truism, but is here critically assessed and found wanting. The case is made that bifilms from [...] Read more.

This paper presents a personal view by the author of the role of bifilms in Al alloys. The mantra ‘microstructure determines properties’ is widely accepted as a truism, but is here critically assessed and found wanting. The case is made that bifilms from the casting process, while often invisible in the microstructure, are usually at least as important, if not of far greater importance, because they are often present as a dense population of cracks throughout the metal. The bifilm population controls the morphology of many features of cast and wrought structures. For cast alloys, bifilm control of pore morphology and Si morphology in Al–Si alloys is discussed, as is dendrite arm spacing (DAS). The tensile property benefits of grain refinement are seen to be mainly bifilm controlled. The properties ductility and fatigue appear to be especially dominated by bifilm content, as are invasive corrosion processes such as pitting, intergranular corrosion, hydrogen blistering and cracking. Bifilm control is proposed as a new concept permitting the improvement and control of metallurgical properties. Full article

(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)

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9 pages, 3798 KiB

Open AccessArticle

Improved Electrical Characteristics of Gallium Oxide/P-Epi Silicon Carbide Static Induction Transistors with UV/Ozone Treatment Fabricated by RF Sputter

by Myeong-Cheol Shin, Young-Jae Lee, Dong-Hyeon Kim, Seung-Woo Jung, Michael A. Schweitz, Weon Ho Shin, Jong-Min Oh, Chulhwan Park and Sang-Mo Koo

Materials 2021, 14(5), 1296; https://doi.org/10.3390/ma14051296 - 8 Mar 2021

Cited by 6 | Viewed by 3439

Abstract

In this study, static induction transistors (SITs) with beta gallium oxide (β-Ga₂O₃) channels are grown on a p-epi silicon carbide (SiC) layer via radio frequency sputtering. The Ga₂O₃ films are subjected to UV/ozone treatment, which results [...] Read more.

In this study, static induction transistors (SITs) with beta gallium oxide (β-Ga₂O₃) channels are grown on a p-epi silicon carbide (SiC) layer via radio frequency sputtering. The Ga₂O₃ films are subjected to UV/ozone treatment, which results in reduced oxygen vacancies in the X-ray photoelectron spectroscopy data, lower surface roughness (3.51 nm) and resistivity (319 Ω·cm), and higher mobility (4.01 cm²V⁻¹s⁻¹). The gate leakage current is as low as 1.0 × 10⁻¹¹ A at V_GS = 10 V by the depletion layer formed between n-Ga₂O₃ and p-epi SiC at the gate region with a PN heterojunction. The UV/O₃-treated SITs exhibit higher (approximately 1.64 × 10² times) drain current (V_DS = 12 V) and on/off ratio (4.32 × 10⁵) than non-treated control devices. Full article

(This article belongs to the Special Issue Physicochemical Properties of Organic and Hybrid Semiconductor Materials)

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19 pages, 2779 KiB

Open AccessArticle

Elaboration and Characterization of Vitreous Fertilizers and Study of Their Impact on the Growth, Photosynthesis, and Yield of Wheat (Triticum durum L.)

by Tariq Labbilta, Mohamed Ait-El-Mokhtar, Younes Abouliatim, Mehdi Khouloud, Abdelilah Meddich and Mohamed Mesnaoui

Materials 2021, 14(5), 1295; https://doi.org/10.3390/ma14051295 - 8 Mar 2021

Cited by 17 | Viewed by 2855

Abstract

Four different phosphate glass formulations (F₀, F₁, F₂, and F₃) were developed according o wheat nutrient requirements to be used as controlled-release fertilizers. These glasses contain macro-elements (P₂O₅-K₂O-CaO-MgO), with [...] Read more.

Four different phosphate glass formulations (F₀, F₁, F₂, and F₃) were developed according o wheat nutrient requirements to be used as controlled-release fertilizers. These glasses contain macro-elements (P₂O₅-K₂O-CaO-MgO), with the addition of microelements (Fe-Mn-Zn-B-Cu-Mo) in each formulation. The effects of these elements’ addition on thermal properties, glass structure, and dissolution behaviors were investigated. Results showed that these glasses are composed essentially of metaphosphate chains and that the addition of micronutrients could change the chemical durability of phosphate glasses. A greenhouse experiment was performed using wheat (Triticum durum L.) to evaluate the efficiency of the four glasses, with or without application of chemical nitrogen (N) (N + VF and VF, respectively). The different formulas were tested using two rates of 0.3 and 1 g per plant. In addition to the vitreous fertilizer formulations, two other treatments were applied: control treatment with no amendment and Nitrogen-Phosphorus-Potassium treatment with the application of the conventional fertilizers on the base of optimal rates. After four months of cultivation, vitreous fertilizers application significantly improved growth (7% to 88%), photosynthetic (8% to 49%) parameters, and yield (29% to 33%) compared to NPK treatment and to the control. It has been found that formulas F₁, F₂, and F₃ may constitute a potential alternative to conventional fertilization due to their positive impact on wheat production and can be used in practice as an environmentally controlled-release fertilizer. Full article

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12 pages, 2458 KiB

Open AccessArticle

Electrical Conductivity of a Stretching Viscoelastic Filament

by Manuel Rubio, Samir Sadek, Emilio José Vega, Alfonso Miguel Gañán-Calvo and José María Montanero

Materials 2021, 14(5), 1294; https://doi.org/10.3390/ma14051294 - 8 Mar 2021

Cited by 6 | Viewed by 2223

Abstract

Long polymeric chains highly stretched and aligned with the flow confer a strong mechanical anisotropy on a viscoelastic solution. The electrically-driven transport of free ions under such conditions is far from being understood. In this paper, we determine experimentally whether the above-mentioned deviation [...] Read more.

Long polymeric chains highly stretched and aligned with the flow confer a strong mechanical anisotropy on a viscoelastic solution. The electrically-driven transport of free ions under such conditions is far from being understood. In this paper, we determine experimentally whether the above-mentioned deviation from isotropy affects the electric charge transport across the liquid. To this end, we measure the electrical conductivity in the flow (stretching) direction of the cylindrical liquid filament formed in the elasto-capillary thinning that arises during the breakup of a viscoelastic liquid bridge. First, we examine the behavior of monodisperse solutions of polyethylene oxide (PEO) in a mixture of glycerine and water. For all the concentrations and molecular weights considered, the filament conductivity remains practically the same as the isotropic conductivity measured under hydrostatic conditions. However, we observe a decrease in the electric current at the end of elasto-capillary regime which may partially be attributed to the reduction of the liquid conductivity. Then, we measure the conductivity of bidisperse solutions of PEO with very different molecular weights. In this case, a significant decrease in conductivity is observed as the filament radius decreases. This constitutes the first experimental evidence of ion mobility reduction in stretching viscoelastic filaments, a relevant effect in applications such as electrospinning. Full article

(This article belongs to the Special Issue Surface-Tension-Driven Flows for Shaping and Fragmenting Matter on the Submillimeter Scale)

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11 pages, 4656 KiB

Open AccessEditor’s ChoiceArticle

Asymmetrical Barkhausen Noise of a Hard Milled Surface

by Mária Čilliková, Anna Mičietová, Robert Čep, Branislav Mičieta, Miroslav Neslušan and Pavel Kejzlar

Materials 2021, 14(5), 1293; https://doi.org/10.3390/ma14051293 - 8 Mar 2021

Cited by 8 | Viewed by 2152

Abstract

This study is focused on the asymmetrical Barkhausen noise emission of a hard milled surface during cyclic magnetisation. The Barkhausen noise is studied as a function of the magnetising voltage and the hard milled surface is compared with a surface after heat treatment. [...] Read more.

This study is focused on the asymmetrical Barkhausen noise emission of a hard milled surface during cyclic magnetisation. The Barkhausen noise is studied as a function of the magnetising voltage and the hard milled surface is compared with a surface after heat treatment. The asymmetry in the Barkhausen noise emission after hard milling occurs due to the typical “sandwich” structure and the different magnetic hardnesses of the different layers beneath the free surface. Furthermore, this asymmetry is also due to the preferential orientation of the matrix in the direction of the cutting speed and magnetostatic fields, which hinder or favour the premagnetising process. Full article

(This article belongs to the Collection Machining and Manufacturing of Alloys and Steels)

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9 pages, 2379 KiB

Open AccessArticle

Effects of Ultrasonic Activation on Root Canal Filling Quality of Single-Cone Obturation with Calcium Silicate-Based Sealer

by Sin-Young Kim, Young-Eun Jang, Bom Sahn Kim, Eun-Kyoung Pang, Kiche Shim, Hye Ryeon Jin, Min Kyung Son and Yemi Kim

Materials 2021, 14(5), 1292; https://doi.org/10.3390/ma14051292 - 8 Mar 2021

Cited by 10 | Viewed by 3126

Abstract

Background: We evaluated the effects of ultrasonic activation on root canal filling quality of the single-cone (SC) obturation technique with calcium silicate sealers and gutta percha cones. Methods: Thirty-six human single-rooted premolars were obturated with gutta percha and sealer. For the continuous wave [...] Read more.

Background: We evaluated the effects of ultrasonic activation on root canal filling quality of the single-cone (SC) obturation technique with calcium silicate sealers and gutta percha cones. Methods: Thirty-six human single-rooted premolars were obturated with gutta percha and sealer. For the continuous wave (CW) group (n = 12), AH Plus with a continuous wave technique was used. The SC group (n = 12) received EndoSequence BC sealer with a single-cone technique. The SCU (SC with the addition of ultrasonic activation) group (n = 12) received the same treatment. Micro-computed tomography was used to scan the teeth, and the void volume within the root canal was evaluated at the apical, middle, and coronal levels. Then cross-sections were observed under a light microscope and scanning electron microscope (SEM). Results: Void volume was significantly lower in the SCU group than in the CW and SC groups. There were no statistically significant differences between the CW and SC groups. The SCU group had fewer voids than the CW and SC groups in the coronal and middle third areas. Specimens showed no apparent gaps or voids in any group. SEM images revealed both gap-free and gap-containing regions at different levels in all groups. Conclusions: Single-cone obturation with calcium silicate-based sealers might obtain enhanced filling quality when used with ultrasonic activation. Full article

(This article belongs to the Special Issue Evaluation of Novel Biomaterials in Endodontics, Periodontics, and Restorative Dentistry)

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