Materials

15 pages, 4123 KiB

Open AccessArticle

Physico-Chemical Surface Modifications of Polyetheretherketone (PEEK) Using Extreme Ultraviolet (EUV) Radiation and EUV-Induced Nitrogen Plasma

by Joanna Czwartos, Bogusław Budner, Andrzej Bartnik, Przemysław Wachulak, Henryk Fiedorowicz and Zygmunt Mierczyk

Materials 2020, 13(19), 4466; https://doi.org/10.3390/ma13194466 - 8 Oct 2020

Cited by 16 | Viewed by 3011

Abstract

In this work, the effect of extreme ultraviolet (EUV) radiation and the combination of EUV radiation and low-temperature nitrogen plasma on the physico-chemical properties of polyetheretherketone (PEEK) surfaces were presented. The laser-plasma EUV source based on a double gas puff target was used [...] Read more.

In this work, the effect of extreme ultraviolet (EUV) radiation and the combination of EUV radiation and low-temperature nitrogen plasma on the physico-chemical properties of polyetheretherketone (PEEK) surfaces were presented. The laser-plasma EUV source based on a double gas puff target was used in this experiment to irradiate PEEK surfaces with nanosecond pulses of EUV radiation and to produce low-temperature plasma through the photoionization of nitrogen with EUV photons. The changes in surface morphology on irradiated polymer samples were examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Chemical changes of the PEEK surfaces were analysed using X-ray photoelectron spectroscopy (XPS). EUV radiation and nitrogen plasma treatment caused significant changes in the topography of modified PEEK’s surfaces and an increase in their average roughness. Strong chemical decomposition, appearance of new functional groups as well as incorporation of nitrogen atoms up to ~17 at.% on the PEEK’s surface were observed. Full article

(This article belongs to the Special Issue Radiation Effect on Polymeric Materials)

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16 pages, 5062 KiB

Open AccessArticle

Surface Evaluation of a Multi-Pass Flexible Magnetic Burnishing Brush for Rough and Soft Ground 60/40 Brass

by Ayman M. Alaskari, Abdulaziz I. Albannai, Meshal Y. Alawadhi, Abdulkareem S. Aloraier, Tatiana Liptakova and Abdullah A. Alazemi

Materials 2020, 13(19), 4465; https://doi.org/10.3390/ma13194465 - 8 Oct 2020

Cited by 3 | Viewed by 1891

Abstract

Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and [...] Read more.

Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and directions on the produced surface of soft and rough ground prepared brass. In total, five different samples were burnished on each of the two brass samples prepared. Four samples were processed in the same direction for up to four passes and the fifth sample was processed with two passes in the opposite direction. Results indicate that there was approximately a 30% increase in hardness and an 83% increase in microroughness for rougher-surface brass samples. For smoothly prepared surfaces, there was approximately a 14% increase in hardness and a 35% increase in microroughness. In the same direction of multi-pass burnishing, increasing the number of passes negatively affected surface roughness; for rougher surfaces, the surface hardness reduced and process uniformity increased owing to surface over-hardening and flaking mechanisms, and for smoother surfaces, the hardness, roughness, and process non-uniformity increased with the number of passes owing to repeated surface deformation at some locations and high flaking at other locations. Compared to single-pass burnishing, wherein the surface roughness and microhardness showed almost no change with high process uniformity, in burnishing with two opposite-direction passes, the produced surface exhibited better surface roughness, process uniformity, and microhardness improvements owing to a reverse strain mechanism. Hence, opposite burnishing passes are recommended. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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14 pages, 27927 KiB

Open AccessArticle

Graphene Oxide Aerosol Deposition and its Influence on Cancer Cells. Preliminary Results

by Barbara Nasiłowska, Zdzisław Bogdanowicz, Kinga Hińcza, Zygmunt Mierczyk, Stanisław Góźdź, Małgorzata Djas, Krystian Kowiorski, Aneta Bombalska and Artur Kowalik

Materials 2020, 13(19), 4464; https://doi.org/10.3390/ma13194464 - 8 Oct 2020

Cited by 18 | Viewed by 2786

Abstract

This paper presents the results of the interaction of graphene oxide (GO) on MDA-MB-231 and SW-954 cancer cell lines. The tests were carried out in two variants. In the first one, GO was sprayed on a Petri dish and then, the cancer cell [...] Read more.

This paper presents the results of the interaction of graphene oxide (GO) on MDA-MB-231 and SW-954 cancer cell lines. The tests were carried out in two variants. In the first one, GO was sprayed on a Petri dish and then, the cancer cell lines were cultured. In the second variant, the cells were covered with an aerosol containing GO. In both variants, cancer cell lines were incubated and tested every 24, 48, and 72 h. After each time period, cell viability and surface morphology were measured. The tests after 72 h showed that coating with GO aerosol caused a reduction in cell viability by 52.7% and 26.4% for MDA-MB-231 and SW-954 cancer cell lines, respectively, with respect to a reference sample (without the influence of GO aerosol). Tests where GO is a culture medium demonstrated a decrease in cell viability by approximately 4.3% compared to a reference sample for both considered cell lines. Full article

(This article belongs to the Special Issue Biomedical and Environmental Applications of Graphene and Graphene Oxide)

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17 pages, 2443 KiB

Open AccessArticle

Thermoelastic Processes by a Continuous Heat Source Line in an Infinite Solid via Moore–Gibson–Thompson Thermoelasticity

by Ahmed E. Abouelregal, Ibrahim-Elkhalil Ahmed, Mohamed E. Nasr, Khalil M. Khalil, Adam Zakria and Fawzy A. Mohammed

Materials 2020, 13(19), 4463; https://doi.org/10.3390/ma13194463 - 8 Oct 2020

Cited by 48 | Viewed by 2701

Abstract

Many attempts have been made to investigate the classical heat transfer of Fourier, and a number of improvements have been implemented. In this work, we consider a novel thermoelasticity model based on the Moore–Gibson–Thompson equation in cases where some of these models fail [...] Read more.

Many attempts have been made to investigate the classical heat transfer of Fourier, and a number of improvements have been implemented. In this work, we consider a novel thermoelasticity model based on the Moore–Gibson–Thompson equation in cases where some of these models fail to be positive. This thermomechanical model has been constructed in combination with a hyperbolic partial differential equation for the variation of the displacement field and a parabolic differential equation for the temperature increment. The presented model is applied to investigate the wave propagation in an isotropic and infinite body subjected to a continuous thermal line source. To solve this problem, together with Laplace and Hankel transform methods, the potential function approach has been used. Laplace and Hankel inverse transformations are used to find solutions to different physical fields in the space–time domain. The problem is validated by calculating the numerical calculations of the physical fields for a given material. The numerical and theoretical results of other thermoelastic models have been compared with those described previously. Full article

(This article belongs to the Special Issue Advances in Mechanical Metamaterials)

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21 pages, 5042 KiB

Open AccessEditor’s ChoiceArticle

Metal Removal from Nickel-Containing Effluents Using Mineral–Organic Hybrid Adsorbent

by Inga Zinicovscaia, Nikita Yushin, Dmitrii Grozdov, Konstantin Vergel, Nadezhda Popova, Grigoriy Artemiev and Alexey Safonov

Materials 2020, 13(19), 4462; https://doi.org/10.3390/ma13194462 - 8 Oct 2020

Cited by 23 | Viewed by 2778

Abstract

Nickel is one of the most dangerous environmental pollutants and its removal from wastewater is an important task. The capacity of a mineral–organic hybrid adsorbent, consisting of Shewanella xiamenensis biofilm and zeolite (clinoptilolite of the Chola deposit), to remove metal ions from nickel-containing [...] Read more.

Nickel is one of the most dangerous environmental pollutants and its removal from wastewater is an important task. The capacity of a mineral–organic hybrid adsorbent, consisting of Shewanella xiamenensis biofilm and zeolite (clinoptilolite of the Chola deposit), to remove metal ions from nickel-containing batch systems under different experimental conditions was tested. The obtained biosorbent was characterized using neutron activation, SEM, and FTIR techniques. It was established that maximum removal of cations, up to 100%, was achieved at pH 6.0. Several mathematical models were applied to describe the equilibrium and kinetics data. The maximum adsorption capacity of the hybrid biosorbent, calculated using the Langmuir model, varied from 3.6 to 3.9 mg/g. Negative Gibbs energy values and positive ∆H° values indicate the spontaneous and endothermic character of the biosorption process. The effects of several parameters (pH and biosorbent dosage) on Ni(II) removal from real effluent, containing nickel with a concentration of 125 mg/L, were investigated. The optimal pH for Ni(II) removal was 5.0–6.0 and an increase of sorbent dosage from 0.5 to 2.0 led to an increase in Ni(II) removal from 17% to 27%. At two times effluent dilution, maximum Ni(II) removal of 26% was attained at pH 6.0 and sorbent dosage of 1.0 g. A 12-fold effluent dilution resulted in the removal of 72% of Ni(II) at the same pH and sorbent dosage values. The obtained hybrid biosorbent can be used for Ni(II) removal from industrial effluents with low Ni(II) concentrations. Full article

(This article belongs to the Special Issue Materials for Heavy Metals Removal from Waters)

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12 pages, 2453 KiB

Open AccessArticle

New Feedstock System for Fused Filament Fabrication of Sintered Alumina Parts

by Dorit Nötzel and Thomas Hanemann

Materials 2020, 13(19), 4461; https://doi.org/10.3390/ma13194461 - 8 Oct 2020

Cited by 43 | Viewed by 3622

Abstract

Only a few 3D-printing techniques are able to process ceramic materials and exploit successfully the capabilities of additive manufacturing of sintered ceramic parts. In this work, a new two component binder system, consisting of polyethyleneglycol and polyvinylbutyral, as well stearic acid as surfactant, [...] Read more.

Only a few 3D-printing techniques are able to process ceramic materials and exploit successfully the capabilities of additive manufacturing of sintered ceramic parts. In this work, a new two component binder system, consisting of polyethyleneglycol and polyvinylbutyral, as well stearic acid as surfactant, was filled with submicron sized alumina up to 55 vol.% and used in fused filament fabrication (FFF) for the first time. The whole process chain, as established in powder injection molding of ceramic parts, starting with material selection, compounding, measurement of shear rate and temperature dependent flow behavior, filament fabrication, as well as FFF printing. A combination of solvent pre-debinding with thermal debinding and sintering at a reduced maximum temperature due to the submicron sized alumina and the related enhanced sinter activity, enabled the realization of alumina parts with complex shape and sinter densities around 98 % Th. Finally the overall shrinkage of the printed parts were compared with similar ones obtained by micro ceramic injection molding. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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17 pages, 9424 KiB

Open AccessArticle

The Effect of Using a Metal Tube on Laser Welding of the Battery Case and the Tab for Lithium-Ion Battery

by Lanh Ngoc Trinh and Dongkyoung Lee

Materials 2020, 13(19), 4460; https://doi.org/10.3390/ma13194460 - 8 Oct 2020

Cited by 11 | Viewed by 4524

Abstract

Given the drawbacks of the conventional welding methods in joining the battery case and tab in the lithium-ion battery, the laser welding technique using the metal tube has been introduced for the weld. The metal tube is supposed to contribute a positive effect [...] Read more.

Given the drawbacks of the conventional welding methods in joining the battery case and tab in the lithium-ion battery, the laser welding technique using the metal tube has been introduced for the weld. The metal tube is supposed to contribute a positive effect including protection to the outside structure by blocking the injection of the spatters, and minimization of the contact gap between the battery case and table. However, the use of the metal tube is believed to cause the plume trapped inside and affect the intensity distribution of the laser gaussian beam. Through the observation and analysis in this study, both advantages and disadvantages of the application of the metal tube on the weld have been analyzed. The use of the metal tube prevents the ejection of the spatter to the outside of the welding zone, as well as minimize the air gap between the battery case and tab in the lap joint weld is also minimized. On the other hand, the trapped plume inside the metal tube and the reduction of the energy of the laser beam have been considered to cause significant changes in the morphology, mechanical, and electrical properties of the weld. Full article

(This article belongs to the Special Issue Advanced Design for Manufacturing Processes)

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13 pages, 4590 KiB

Open AccessArticle

Effect of Halloysite Nanotube on Mechanical Properties, Thermal Stability and Morphology of Polypropylene and Polypropylene/Short Kenaf Fibers Hybrid Biocomposites

by Piotr Franciszczak, Iman Taraghi, Sandra Paszkiewicz, Maksymilian Burzyński, Agnieszka Meljon and Elżbieta Piesowicz

Materials 2020, 13(19), 4459; https://doi.org/10.3390/ma13194459 - 8 Oct 2020

Cited by 19 | Viewed by 2561

Abstract

In this article, the effect of the addition of halloysite nanotube (HNT) on the mechanical and thermal stability of polypropylene (PP) and PP/kenaf fiber biocomposites has been investigated. Different volume contents of HNTs ranging from 1 to 10 vol.% were melt mixed with [...] Read more.

In this article, the effect of the addition of halloysite nanotube (HNT) on the mechanical and thermal stability of polypropylene (PP) and PP/kenaf fiber biocomposites has been investigated. Different volume contents of HNTs ranging from 1 to 10 vol.% were melt mixed with PP and PP/kenaf fibers. The volume content of kenaf fibers was kept constant at 30%. The morphology of HNTs within the PP matrix has been studied via scanning electron microscopy (SEM). The morphological results revealed that HNT was uniformly dispersed in the PP matrix already at a low concentration of 1 and 2 vol.%. The mechanical properties of the manufactured nanocomposites and hybrid biocomposites such as Young’s modulus, tensile strength, elongation at break, flexural modulus, flexural strength, and notched Izod strength have been measured. The results show that Young’s modulus and strengths have been improved along with the addition of low content of HNTs. Moreover, the gain of notched Izod impact strength obtained by the addition of short kenaf fibers was maintained in hybrids with low concentrations of HNTs. Finally, the thermogravimetric analysis shows that at 10% and 50% weight loss, the thermal degradation rate of the PP and PP/kenaf biocomposites decreased by the addition of HNTs. Full article

(This article belongs to the Special Issue Functionalization, Characterization, and Applications of Polymeric and Hybrid Materials)

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27 pages, 11530 KiB

Open AccessArticle

A Numerical Wear Simulation Method of Reciprocating Seals with a Textured Rod

by Hongliang Ran, Di Liu and Shaoping Wang

Materials 2020, 13(19), 4458; https://doi.org/10.3390/ma13194458 - 8 Oct 2020

Cited by 7 | Viewed by 3260

Abstract

Reciprocating rod seals are widely used in the hydraulic actuator to prevent the leakage of fluid. The sealing lip profile changes with the seal wear, resulting in an increase in the leakage. A texturing rod changes the lubrication characteristics of the seal, so [...] Read more.

Reciprocating rod seals are widely used in the hydraulic actuator to prevent the leakage of fluid. The sealing lip profile changes with the seal wear, resulting in an increase in the leakage. A texturing rod changes the lubrication characteristics of the seal, so it affects the wear and leakage of the seal. A numerical simulation method is proposed to investigate the wear of the hydraulic reciprocating seal with textured rods. Several kinds of macro-cavity textures on the rod surface, including circle, square and triangle shapes, have been simulated and discussed. The effects of three shape parameters including area ratio, depth, and ratio of the axial length to the circumferential length on the seal wear are analyzed in detail. The texturing rod slightly increases the seal wear, but decreases the seal leakage. When the rod speed is increasing, the wear time rates of the seal increase, while the wear distance rates decrease, regardless of the texture shapes. When the texture area ratio is increasing, the wear of the reciprocating seal increases. Seal wear decreases with an increasing texture depth during the outstroke, however, it increases during the instroke. The ratio of the axial length of the macro-cavity to the circumferential length has no effect on the seal wear. Full article

(This article belongs to the Special Issue Friction and Wear of Materials Surfaces)

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22 pages, 41297 KiB

Open AccessArticle

Processing of Polyester-Urethane Filament and Characterization of FFF 3D Printed Elastic Porous Structures with Potential in Cancellous Bone Tissue Engineering

by Agnieszka Haryńska, Iga Carayon, Paulina Kosmela, Anna Brillowska-Dąbrowska, Marcin Łapiński, Justyna Kucińska-Lipka and Helena Janik

Materials 2020, 13(19), 4457; https://doi.org/10.3390/ma13194457 - 8 Oct 2020

Cited by 24 | Viewed by 4164

Abstract

This paper addresses the potential of self-made polyester-urethane filament as a candidate for Fused Filament Fabrication (FFF)-based 3D printing (3DP) in medical applications. Since the industry does not provide many ready-made solutions of medical-grade polyurethane filaments, we undertook research aimed at presenting the [...] Read more.

This paper addresses the potential of self-made polyester-urethane filament as a candidate for Fused Filament Fabrication (FFF)-based 3D printing (3DP) in medical applications. Since the industry does not provide many ready-made solutions of medical-grade polyurethane filaments, we undertook research aimed at presenting the process of thermoplastic polyurethane (TPU) filament formation, detailed characteristics, and 3DP of specially designed elastic porous structures as candidates in cancellous tissue engineering. Additionally, we examined whether 3D printing affects the structure and thermal stability of the filament. According to the obtained results, the processing parameters leading to the formation of high-quality TPU filament (TPU_F) were captured. The results showed that TPU_F remains stable under the FFF 3DP conditions. The series of in vitro studies involving long- and short-term degradation (0.1 M phosphate-buffered saline (PBS); 5 M sodium hydroxide (NaOH)), cytotoxicity (ISO 10993:5) and bioactivity (simulated body fluid (SBF) incubation), showed that TPU printouts possessing degradability of long-term degradable tissue constructs, are biocompatible and susceptible to mineralization in terms of hydroxyapatite (HAp) formation during SBF exposure. The formation of HAp on the surface of the specially designed porous tissue structures (PTS) was confirmed by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) studies. The compression test of PTS showed that the samples were strengthened due to SBF exposure and deposited HAp on their surface. Moreover, the determined values of the tensile strength (~30 MPa), Young’s modulus (~0.2 GPa), and compression strength (~1.1 MPa) allowed pre-consideration of TPU_F for FFF 3DP of cancellous bone tissue structures. Full article

(This article belongs to the Special Issue Additive Manufacturing (AM) of Biomaterials)

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18 pages, 17435 KiB

Open AccessArticle

Altering the Elastic Properties of 3D Printed Poly-Lactic Acid (PLA) Parts by Compressive Cyclic Loading

by Tomaž Pepelnjak, Ako Karimi, Andraž Maček and Nikolaj Mole

Materials 2020, 13(19), 4456; https://doi.org/10.3390/ma13194456 - 8 Oct 2020

Cited by 13 | Viewed by 3020

Abstract

In designing high-performance, lightweight components, cellular structures are one of the approaches to be considered. The present study aimed to analyze the effect of the infill line distance of 3D printed circular samples on their compressive elastic behavior. Lightweight cellular poly-lactic acid (PLA) [...] Read more.

In designing high-performance, lightweight components, cellular structures are one of the approaches to be considered. The present study aimed to analyze the effect of the infill line distance of 3D printed circular samples on their compressive elastic behavior. Lightweight cellular poly-lactic acid (PLA) samples with a triangular infill pattern were exposed to cyclic compressive loading and their stiffness was investigated. PLA is one of the most commonly used thermoplastic materials in additive manufacturing using the fused filament fabrication (FFF) process. Cylindrical samples with a diameter of 11.42 mm and a height of 10 mm were printed using FFF technology with two different infill line distances (1.6 mm and 2.4 mm). Comparing the nominal compressive stress-nominal strain curves under cyclic loading showed that the first cycle response was significantly different with respect to the subsequent ones. Furthermore, an analysis of the dependence of the modulus of elasticity on the effects of cyclic loading was performed. It was found that through elastic deformation, and combined elastic and plastic deformation, the samples’ properties such as stiffness could be altered. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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12 pages, 3915 KiB

Open AccessArticle

Effect of the Anisotropy Mechanical Properties on LN Crystals Fixed-Abrasive Lapping

by Nannan Zhu, Jiapeng Chen, Piao Zhou and Yongwei Zhu

Materials 2020, 13(19), 4455; https://doi.org/10.3390/ma13194455 - 8 Oct 2020

Cited by 1 | Viewed by 2041

Abstract

The anisotropy of lithium niobate (LN) single crystals in mechanical properties affects its material removal uniformity during lapping. The nano-indentation hardness (H_I) and elastic modulus(E) of Z-cut wafer and X-cut wafer were measured by a nano-indentation tester. The [...] Read more.

The anisotropy of lithium niobate (LN) single crystals in mechanical properties affects its material removal uniformity during lapping. The nano-indentation hardness (H_I) and elastic modulus(E) of Z-cut wafer and X-cut wafer were measured by a nano-indentation tester. The nano-scratching tests were adopted to evaluate its critical cutting depth (d_c) of brittle ductile transition along crucial orientations of Z-cut and X-cut, respectively. A series of fixed-abrasive lapping tests were carried out to explore the effect of anisotropy on the lapping process. The results indicated that the H_I of Z-cut was slightly higher than that of X-cut, while the E of Z-cut was about 1.1 times of the latter. The d_c value of each orientation varies greatly. The lapping tests showed that the material removal rate (MRR) of Z-cut was lower than that of X-cut, for its high H_I and E. Meanwhile, the surface quality of Z-cut was better than that of X-cut, for the larger d_c of Z-cut. The research of mechanical properties of LN has guiding significance for its lapping process. Full article

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37 pages, 1577 KiB

Open AccessFeature PaperReview

Biologically Active Compounds of Plants: Structure-Related Antioxidant, Microbiological and Cytotoxic Activity of Selected Carboxylic Acids

by Beata Godlewska-Żyłkiewicz, Renata Świsłocka, Monika Kalinowska, Aleksandra Golonko, Grzegorz Świderski, Żaneta Arciszewska, Edyta Nalewajko-Sieliwoniuk, Monika Naumowicz and Włodzimierz Lewandowski

Materials 2020, 13(19), 4454; https://doi.org/10.3390/ma13194454 - 8 Oct 2020

Cited by 63 | Viewed by 7899

Abstract

Natural carboxylic acids are plant-derived compounds that are known to possess biological activity. The aim of this review was to compare the effect of structural differences of the selected carboxylic acids (benzoic acid (BA), cinnamic acid (CinA), p-coumaric acid (p-CA), caffeic [...] Read more.

Natural carboxylic acids are plant-derived compounds that are known to possess biological activity. The aim of this review was to compare the effect of structural differences of the selected carboxylic acids (benzoic acid (BA), cinnamic acid (CinA), p-coumaric acid (p-CA), caffeic acid (CFA), rosmarinic acid (RA), and chicoric acid (ChA)) on the antioxidant, antimicrobial, and cytotoxic activity. The studied compounds were arranged in a logic sequence of increasing number of hydroxyl groups and conjugated bonds in order to investigate the correlations between the structure and bioactivity. A review of the literature revealed that RA exhibited the highest antioxidant activity and this property decreased in the following order: RA > CFA ~ ChA > p-CA > CinA > BA. In the case of antimicrobial properties, structure-activity relationships were not easy to observe as they depended on the microbial strain and the experimental conditions. The highest antimicrobial activity was found for CFA and CinA, while the lowest for RA. Taking into account anti-cancer properties of studied NCA, it seems that the presence of hydroxyl groups had an influence on intermolecular interactions and the cytotoxic potential of the molecules, whereas the carboxyl group participated in the chelation of endogenous transition metal ions. Full article

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

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10 pages, 1996 KiB

Open AccessArticle

The Influence of UV Light on Rheological Properties of Collagen Extracted from Silver Carp Skin

by Alina Sionkowska, Katarzyna Lewandowska and Katarzyna Adamiak

Materials 2020, 13(19), 4453; https://doi.org/10.3390/ma13194453 - 8 Oct 2020

Cited by 23 | Viewed by 3204

Abstract

Acid soluble collagen (ASC) was extracted from Silver Carp fish skin. Collagen was dissolved in acetic acid at varying concentrations and its rheological properties were studied. Steady shear flow properties of collagen solutions at concentrations of 5 and 10 mg/mL were characterized using [...] Read more.

Acid soluble collagen (ASC) was extracted from Silver Carp fish skin. Collagen was dissolved in acetic acid at varying concentrations and its rheological properties were studied. Steady shear flow properties of collagen solutions at concentrations of 5 and 10 mg/mL were characterized using rheometry at 20 °C. Collagen solutions were irradiated with UV light (wavelength 254 nm) for up to 2 h and rheological properties were measured. All the collagen solutions showed a shear-thinning flow behavior. A constant viscosity region was observed after 1 h of UV irradiation, which showed that collagen molecules were fully denatured. A short treatment with collagen solution by UV (ultraviolet) light led to an increase in viscosity; however, the denaturation temperature of UV-irradiated collagen decreased. Depending on the time of UV treatment, collagen extracted from Silver Carp fish skin may undergo physical crosslinking or photodegradation. Physically crosslinked collagen may find applications in functional food, cosmetic, biomedical, and pharmaceutical industries. Full article

(This article belongs to the Special Issue Collagens, Collagen-Based and Collagen-Mimetic Biomaterials: Preparation, Characterization and Applications)

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24 pages, 29382 KiB

Open AccessArticle

Analysis of γ′ Precipitates, Carbides and Nano-Borides in Heat-Treated Ni-Based Superalloy Using SEM, STEM-EDX, and HRSTEM

by Łukasz Rakoczy, Bogdan Rutkowski, Małgorzata Grudzień-Rakoczy, Rafał Cygan, Wiktoria Ratuszek and Anna Zielińska-Lipiec

Materials 2020, 13(19), 4452; https://doi.org/10.3390/ma13194452 - 8 Oct 2020

Cited by 20 | Viewed by 5056

Abstract

The microstructure of a René 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 °C-2h) and aged (900 °C-8h). The γ [...] Read more.

The microstructure of a René 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 °C-2h) and aged (900 °C-8h). The γ matrix is mainly strengthened by the ordered L1₂ γ′ phase, with the mean γ/γ′ misfit, δ, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary γ′ precipitates. At the interface of the matrix with secondary γ′ precipitates, nano M₅B₃ borides are present. In the interdendritic spaces additionally primary γ′ precipitates, MC and nano M₂₃C₆ carbides were detected. The γ′ precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of γ′-formers occurs in coarse γ′ surrounding MC carbides. Borides M₅B₃ contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate’s morphology. The nano M₂₃C₆ carbides enriched in Cr have been formed as a consequence of phase transformation MC + γ → M₂₃C₆ + γ′ during the ageing treatment. Full article

(This article belongs to the Special Issue Novel Material and Technological Solutions in Foundry Engineering)

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13 pages, 3489 KiB

Open AccessArticle

Strength, Drying Shrinkage, and Carbonation Characteristic of Amorphous Metallic Fiber-Reinforced Mortar with Artificial Lightweight Aggregate

by Se-Jin Choi, Ji-Hwan Kim, Sung-Ho Bae and Tae-Gue Oh

Materials 2020, 13(19), 4451; https://doi.org/10.3390/ma13194451 - 7 Oct 2020

Cited by 8 | Viewed by 2169

Abstract

This paper investigates the strength, drying shrinkage, and carbonation characteristic of amorphous metallic fiber-reinforced mortar with natural and artificial lightweight aggregates. The use of artificial lightweight aggregates has the advantage of reducing the unit weight of the mortar or concrete, but there is [...] Read more.

This paper investigates the strength, drying shrinkage, and carbonation characteristic of amorphous metallic fiber-reinforced mortar with natural and artificial lightweight aggregates. The use of artificial lightweight aggregates has the advantage of reducing the unit weight of the mortar or concrete, but there is a concern that mechanical properties of concrete such as compressive strength and tensile strength may deteriorate due to the porous properties of lightweight aggregates. In order to improve the mechanical properties of lightweight aggregate mortar, we added 0, 10, 20, and 30 kg/m³ of amorphous metallic fibers to the samples with lightweight aggregate; the same amount of fiber was applied to the samples with natural aggregate for comparison. According to this investigation, the flow of mortar decreased as the amount of amorphous metallic fiber increased, regardless of the aggregate type. The compressive strength of lightweight aggregate mortar with 10 kg/m³ amorphous metallic fiber was similar to that of the LAF0 sample without amorphous metallic fiber after 14 days. In addition, the flexural strength of the samples increased as the amount of amorphous metallic fiber increased. The highest 28-d flexural strength was obtained as approximately 9.28 MPa in the LAF3 sample, which contained 30 kg/m³ amorphous metallic fiber. The drying shrinkage of the samples with amorphous metallic fiber was smaller than that of the sample without amorphous metallic fiber. Full article

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

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13 pages, 1835 KiB

Open AccessArticle

High-Voltage Lithium-Ion Battery Using Substituted LiCoPO₄: Electrochemical and Safety Performance of 1.2 Ah Pouch Cell

by Dongqiang Liu, Chisu Kim, Alexis Perea, Dubé Joël, Wen Zhu, Steve Collin-Martin, Amélie Forand, Martin Dontigny, Catherine Gagnon, Hendrix Demers, Samuel Delp, Jan Allen, Richard Jow and Karim Zaghib

Materials 2020, 13(19), 4450; https://doi.org/10.3390/ma13194450 - 7 Oct 2020

Cited by 8 | Viewed by 3458

Abstract

A LiCoPO₄-based high-voltage lithium-ion battery was fabricated in the format of a 1.2 Ah pouch cell that exhibited a highly stable cycle life at a cut-off voltage of 4.9 V. The high-voltage stability was achieved using a Fe-Cr-Si multi-ion-substituted LiCoPO₄ [...] Read more.

A LiCoPO₄-based high-voltage lithium-ion battery was fabricated in the format of a 1.2 Ah pouch cell that exhibited a highly stable cycle life at a cut-off voltage of 4.9 V. The high-voltage stability was achieved using a Fe-Cr-Si multi-ion-substituted LiCoPO₄ cathode and lithium bis(fluorosulfonyl)imide in 1-methyl-1-propylpyrrolidinium bis(fluorosulfony)imide as the electrolyte. Due to the improved electrochemical stability at high voltage, the cell exhibited a stable capacity retention of 91% after 290 cycles without any gas evolution related to electrolyte decomposition at high voltage. In addition to improved cycling stability, the nominal 5 V LiCoPO₄ pouch cell also exhibited excellent safety performance during a nail penetration safety test compared with a state-of-the-art lithium ion battery. Meanwhile, the thermal stabilities of the 1.2 Ah pouch cell as well as the delithiated LiCoPO₄ were also studied by accelerating rate calorimetry (ARC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and in situ X-ray diffraction (XRD) analyses and reported. Full article

(This article belongs to the Special Issue Electrochemical Materials in Batteries)

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20 pages, 6420 KiB

Open AccessArticle

Tailoring the Surface Morphology and the Crystallinity State of Cu- and Zn-Substituted Hydroxyapatites on Ti and Mg-Based Alloys

by Konstantin A. Prosolov, Vladimir V. Lastovka, Olga A. Belyavskaya, Dmitry V. Lychagin, Juergen Schmidt and Yurii P. Sharkeev

Materials 2020, 13(19), 4449; https://doi.org/10.3390/ma13194449 - 7 Oct 2020

Cited by 12 | Viewed by 2344

Abstract

Titanium-based alloys are known as a “gold standard” in the field of implantable devices. Mg-based alloys, in turn, are very promising biocompatible material for biodegradable, temporary implants. However, the clinical application of Mg-based alloys is currently limited due to the rapid resorption rate [...] Read more.

Titanium-based alloys are known as a “gold standard” in the field of implantable devices. Mg-based alloys, in turn, are very promising biocompatible material for biodegradable, temporary implants. However, the clinical application of Mg-based alloys is currently limited due to the rapid resorption rate in the human body. The deposition of a barrier layer in the form of bioactive calcium phosphate coating is proposed to decelerate Mg-based alloys resorption. The dissolution rate of calcium phosphates is strongly affected by their crystallinity and structure. The structure of antibacterial Cu- and Zn-substituted hydroxyapatite deposited by an radiofrequency (RF) magnetron sputtering on Ti and Mg–Ca substrates is tailored by post-deposition heat treatment and deposition at increased substrate temperatures. It is established that upon an increase in heat treatment temperature mean crystallite size decreases from 47 ± 17 to 13 ± 9 nm. The character of the crystalline structure is not only governed by the temperature itself but relies on the condition such as either post-deposition treatment, where an amorphous calcium phosphate undergoes crystallization or instantaneous crystalline coating growth during deposition on the hot substrate. A higher treatment temperature at 700 °C results in local coating micro-cracking and induced defects, while the temperature of 400–450 °C resulted in the formation of dense, void-free structure. Full article

(This article belongs to the Special Issue Recent Advances in Biocoatings)

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23 pages, 2052 KiB

Open AccessArticle

Numerical Considerations in the Modeling of a High Explosive Cylinder Experiment Using an ALE Continuum Mechanics Code

by Marvin A. Zocher and Tariq D. Aslam

Materials 2020, 13(19), 4448; https://doi.org/10.3390/ma13194448 - 7 Oct 2020

Cited by 1 | Viewed by 1852

Abstract

A series of experiments involving the detonation of PBX 9501 encased in a copper cylinder are modeled with the objective of evaluating a proposed set of phenomenological parameters for the Wescott–Stewart–Davis reactive burn model. The numerical analysis is conducted using the Los Alamos [...] Read more.

A series of experiments involving the detonation of PBX 9501 encased in a copper cylinder are modeled with the objective of evaluating a proposed set of phenomenological parameters for the Wescott–Stewart–Davis reactive burn model. The numerical analysis is conducted using the Los Alamos continuum mechanics code FLAG. Numerical considerations pertaining to various aspects of modeling the experiments using FLAG are discussed. It is shown that use of the proposed set of phenomenological parameters results in predictions of free-surface velocity that match empirically measured velocities reasonably well. Full article

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15 pages, 3364 KiB

Open AccessArticle

Structural and Chemical Hierarchy in Hydroxyapatite Coatings

by Karlis A. Gross, Christiane Petzold, Liene Pluduma-LaFarge, Maris Kumermanis and Håvard J. Haugen

Materials 2020, 13(19), 4447; https://doi.org/10.3390/ma13194447 - 7 Oct 2020

Cited by 7 | Viewed by 2621

Abstract

Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce [...] Read more.

Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH⁻ ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces. Full article

(This article belongs to the Special Issue Bioactive Ceramics and Their Applications)

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20 pages, 4102 KiB

Open AccessArticle

High and Low Temperature Performance and Fatigue Properties of Silica Fume/SBS Compound Modified Asphalt

by Xuewen Zheng, Wenyuan Xu, Huimin Feng and Kai Cao

Materials 2020, 13(19), 4446; https://doi.org/10.3390/ma13194446 - 7 Oct 2020

Cited by 13 | Viewed by 2383

Abstract

In order to study the high and low temperature properties, and fatigue properties, of silica fume/SBS (Styrene-Butadiene-Styrene) compound modified asphalt (SFSCMA), dynamic shear rheometer (DSR) and bending beam rheometer (BBR) are used to study matrix asphalt (MA), silica fume modified asphalt (SFMA) (silica [...] Read more.

In order to study the high and low temperature properties, and fatigue properties, of silica fume/SBS (Styrene-Butadiene-Styrene) compound modified asphalt (SFSCMA), dynamic shear rheometer (DSR) and bending beam rheometer (BBR) are used to study matrix asphalt (MA), silica fume modified asphalt (SFMA) (silica fume (SF) 6%), SBS modified asphalt (SBSMA) (mass ratio of SBS to Matrix asphalt 4%), and silica fume/SBS compound modified asphalt, and the high temperature rheological properties of silica fume/SBS compound modified asphalt with different silica fume additions are also studied. The modification mechanism of SFSCMA was studied by scanning electron microscope (SEM). The investigation results turn out: along with the increase in the content of SF, the high temperature performance of SFSCMA is improved significantly. When the content of SF is 6%, the high temperature performance is the best. When the content of SF is more than 6%, the high temperature property of SFSCMA is lower than that of SBSMA. It is suggested to choose 6% as the content of SF. Compared with MA, SFMA, and SBSMA, SFSCMA has excellent high temperature performance; compared with MA and SFMA, the low temperature performance of SFSCMA is improved, but it is worse than that of SBSMA. Moreover, when the temperature is lower than −30 °C, its low temperature performance is close to that of MA, or even worse than that of MA. After the compound modification of SF and SBSMA, the fatigue properties of the asphalt are improved, and the fatigue performance of SFSCMA is the best among the four kinds of asphalt. There is a cross-linking force in the network structure of SFSCMA, which restrains the flow of the whole system, so that the stability of the compound modified asphalt is significantly improved, which is favorable to the high temperature performance and fatigue resistance of the compound modified asphalt. However, due to its low mobility, it has a negative impact on the low temperature performance of the compound modified asphalt. In addition, according to previous studies, compared with diatomite, it is proven that SF can reach the same level as diatomite in improving the high temperature performance and fatigue performance of asphalt. Therefore, SF can be used as a good choice of asphalt modifier and can achieve the purpose of waste recycling and environmental protection. Full article

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

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15 pages, 2829 KiB

Open AccessArticle

Configuration of Novel Experimental Fractographic Reverse Engineering Approach Based on Relationship between Spectroscopy of Ruptured Surface and Fracture Behaviour of Rubber Sample

by Sanjoy Datta, Radek Stoček, Evghenii Harea, Ondřej Kratina and Martin Stěnička

Materials 2020, 13(19), 4445; https://doi.org/10.3390/ma13194445 - 7 Oct 2020

Cited by 2 | Viewed by 1947

Abstract

A novel fractographic approach based on a combination of (i) mechanical behavior of cured rubber in uniaxial tensile loading and (ii) spectroscopy of fracture on a ruptured surface was experimentally validated. This approach related the migration of paraffin oil from a matrix to [...] Read more.

A novel fractographic approach based on a combination of (i) mechanical behavior of cured rubber in uniaxial tensile loading and (ii) spectroscopy of fracture on a ruptured surface was experimentally validated. This approach related the migration of paraffin oil from a matrix to the ruptured rubber surface, to the tearing energy related to the deformation speed responsible for total rubber sample rupture, and the approach itself was configured experimentally. It was evaluated on cured natural rubber (NR) for two different paraffin oil concentrations. Single edge notched tensile (SENT) samples were subjected to uniaxial tensile loadings at two different deformation speeds. First, the tearing energy as a function of deformation speed was determined for each defined oil concentration. Secondly, at specific locations on the ruptured surfaces, infrared (IR) spectroscopy was performed to quantify a characteristic absorbance peak height of migrated paraffin oil during the rupture process. The results of the IR analyses were related to the deformation speed to understand the relation between the amount of migrated paraffin oil during the fracture process and the deformation speed which brought about such a fracture. This novel approach enhanced the reverse engineering process of rubber fracture related to the cause of tearing energies during critical failure. Full article

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9 pages, 1734 KiB

Open AccessArticle

Simple Model for Corrugation in Surface Alloys Based on First-Principles Calculations

by Monika Nur, Naoya Yamaguchi and Fumiyuki Ishii

Materials 2020, 13(19), 4444; https://doi.org/10.3390/ma13194444 - 7 Oct 2020

Cited by 5 | Viewed by 2722

Abstract

The structural stability of M/Ag(111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

surface alloys is systematically investigated by using first-principles calculations, where M is a member of group III (B, Al, Ga, In, Tl), IV (C, Si, Ge, Sn, Pb), and V [...] Read more.

The structural stability of M/Ag(111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

surface alloys is systematically investigated by using first-principles calculations, where M is a member of group III (B, Al, Ga, In, Tl), IV (C, Si, Ge, Sn, Pb), and V (N, P, As, Sb, Bi) elements. We focus on the corrugation parameter d which is determined by the height of the M atom from the Ag atom in the plane of the top-most atom, and the relation between atomic radii and corrugations in M/Ag(111) is obtained. The tendencies of the corrugation parameter d can be understood by using a simple hard spherical atomic model. We introduce a new type of atomic radii determined by the corrugation in surface alloys, surface alloy atomic radii, which can be useful for rapid predictions of the structures of surface alloys, not only for M/Ag (111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

systems but also for other surface alloys. Full article

(This article belongs to the Section Materials Physics)

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11 pages, 6898 KiB

Open AccessArticle

The Microstructure, Thermal, and Mechanical Properties of Sn-3.0Ag-0.5Cu-xSb High-Temperature Lead-Free Solder

by Chaojun Li, Yanfu Yan, Tingting Gao and Guodong Xu

Materials 2020, 13(19), 4443; https://doi.org/10.3390/ma13194443 - 7 Oct 2020

Cited by 22 | Viewed by 3281

Abstract

To obtain Sn-3.0Ag-0.5Cu-xSb (x = 0, 25, 28, and 31) high-temperature lead-free solder antimony was added to Sn-3.0Ag-0.5Cu solder. The microstructure, thermal properties, and mechanical behavior of the solder alloy prepared were studied by using JSM-5610LV scanning electron microscope, Germany [...] Read more.

To obtain Sn-3.0Ag-0.5Cu-xSb (x = 0, 25, 28, and 31) high-temperature lead-free solder antimony was added to Sn-3.0Ag-0.5Cu solder. The microstructure, thermal properties, and mechanical behavior of the solder alloy prepared were studied by using JSM-5610LV scanning electron microscope, Germany STA409PC differential scanning calorimeter, AG-I250KN universal tensile testing machine, and other methods. The SEM-EDS results showed that after adding Sb, SnSb phase was formed in the β-Sn matrix phase. The newly formed SnSb phase and the existing Sb in the solder alloy can inhibit the generation of IMC and refine the IMC layer. The addition of Sb significantly increased the melting temperature of the solder alloy. Among them, the thermal performance of Sn-3.0Ag-0.5Cu-25Sb is the best. The melting temperature of Sn-3.0Ag-0.5Cu-25Sb is 332.91 °C and the solid–liquid line range of Sn-3.0Ag-0.5Cu-25Sb solder alloy is 313.28–342.02 °C. Its pasty range is 28.74 °C, lower than 30 °C, which is beneficial for soldering. The test results of the mechanical behavior of Sn-3.0Ag-0.5Cu-xSb solder alloy show that with the increase of Sb addition, the ultimate tensile strength of the solder alloy also increases. However, the change of the elongation of the solder alloy is the opposite. The ultimate tensile strength of the solder alloy increased from 29.45 MPa of Sn-3.0Ag-0.5Cu solder to 70.81 MPa of Sn-3.0Ag-0.5Cu-31Sb solder. The reason for the increase in the strength of the solder alloy is the reduction of the thickness of IMC and the solid solution hardening effect of Sb. Full article

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10 pages, 3462 KiB

Open AccessArticle

Dilatometric and Microstructural Study of Martensite Tempering in 4% Mn Steel

by Adam Grajcar, Mateusz Morawiec, Jose Antonio Jimenez and Carlos Garcia-Mateo

Materials 2020, 13(19), 4442; https://doi.org/10.3390/ma13194442 - 7 Oct 2020

Cited by 7 | Viewed by 2385

Abstract

This paper presents the results of martensite tempering resistance in 4% Mn steel. The material was quenched and tempered at 350 °C for 15, 30, and 60 min. The analysis of the quenching and tempering was carried out using dilatometric and microstructural approaches. [...] Read more.

This paper presents the results of martensite tempering resistance in 4% Mn steel. The material was quenched and tempered at 350 °C for 15, 30, and 60 min. The analysis of the quenching and tempering was carried out using dilatometric and microstructural approaches. The phase composition was assessed using X-ray diffraction. The M_s temperature and tempering progress were simulated using JMatPro software. The dilatometric analysis revealed a small decrease in the relative change in length (RCL) during tempering. This decrease was connected to the precipitation kinetics of cementite within the martensite laths. The microstructure investigation using a scanning electron microscope showed a very small amount of carbides, even for the longest tempering time. This showed the high tempering resistance of the martensite in medium-Mn steels. The hardness results showed an insignificant decrease in the hardness depending on the tempering time, which confirmed the high tempering resistance of martensite. Full article

(This article belongs to the Special Issue Effects of Temperature and Strain Rate on Steel Strengthening)

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18 pages, 7643 KiB

Open AccessArticle

Synthesis and Characterization of Cu₂FeSnS₄–Cu₂MnSnS₄ Solid Solution Microspheres

by Edyta Waluś, Maciej Manecki and Grzegorz Cios

Materials 2020, 13(19), 4440; https://doi.org/10.3390/ma13194440 - 7 Oct 2020

Cited by 10 | Viewed by 2298

Abstract

In this study, we used a hydrothermal method to synthesize microspheres of Cu₂(Mn_1−xFe_x)SnS₄ solid solution (X = 1, 0.8, 0.6, 0.4, 0.2, 0). The process was optimized to improve the crystallinity, morphology, and purity of the [...] Read more.

In this study, we used a hydrothermal method to synthesize microspheres of Cu₂(Mn_1−xFe_x)SnS₄ solid solution (X = 1, 0.8, 0.6, 0.4, 0.2, 0). The process was optimized to improve the crystallinity, morphology, and purity of the obtained materials. All samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The following conditions were optimized: A mixture of water and ethylene glycol at the ratio of 1:7 as the reaction medium, polyvinylpyrrolidone (PVP) as the surface ligand, and reaction temperature of 195 °C for 7 days. The product of synthesis precipitated in the form of aggregates of nanocrystals, which form homogeneous, often concentric microspheres with a diameter of 1–1.5 μm. The chemical composition of the product can be well controlled by the chemical composition of the reactants. The compound Cu₂(Mn_1−xFe_x)SnS₄ forms a continuous series of solid solutions. Full article

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12 pages, 4190 KiB

Open AccessArticle

Topotactic Oxidation of Perovskites to Novel SrMo_1-xM_xO_4−δ (M = Fe and Cr) Deficient Scheelite-Type Oxides

by V. Cascos, R. Martínez-Coronado, M. T. Fernández-Díaz and J. A. Alonso

Materials 2020, 13(19), 4441; https://doi.org/10.3390/ma13194441 - 6 Oct 2020

Cited by 1 | Viewed by 2108

Abstract

New polycrystalline SrMo_1−xM_xO_4−δ (M = Fe and Cr) scheelite oxides have been prepared by topotactical oxidation, by annealing in air at 500 °C, from precursor perovskites with the stoichiometry SrMo_1−xM_xO_3−δ (M = Fe [...] Read more.

New polycrystalline SrMo_1−xM_xO_4−δ (M = Fe and Cr) scheelite oxides have been prepared by topotactical oxidation, by annealing in air at 500 °C, from precursor perovskites with the stoichiometry SrMo_1−xM_xO_3−δ (M = Fe and Cr). An excellent reversibility between the oxidized Sr(Mo,M)O_4−δ scheelite and the reduced Sr(Mo,M)O_3−δ perovskite phase accounts for the excellent behavior of the latter as anode material in solid-oxide fuel cells. A characterization by X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) has been carried out to determine the crystal structure features. The scheelite oxides are tetragonal, space group I4₁/a (No. 88). The Rietveld-refinement from NPD data at room temperature shows evidence of oxygen vacancies in the structure, due to the introduction of Fe³⁺/Cr⁴⁺ cations in the tetrahedrally-coordinated B sublattice, where Mo is hexavalent. A thermal analysis of the reduced perovskite (SrMo_1−xM_xO_3−δ) in oxidizing conditions confirms the oxygen stoichiometry obtained by NPD data; the stability range of the doped oxides, below 400–450 °C, is lower than that for the parent SrMoO₃ oxide. The presence of a Mo⁴⁺/Mo⁵⁺ mixed valence in the reduced SrMo_1−xM_xO_3−δ perovskite oxides confers greater instability against oxidation compared with the parent oxide. Finally, an XPS study confirms the surface oxidation states of Mo, Fe, and Cr in the oxidized samples SrMo_0.9Fe_0.1O_4-δ and SrMo_0.8Cr_0.2O_4-δ. Full article

(This article belongs to the Section Advanced Materials Characterization)

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17 pages, 6319 KiB

Open AccessArticle

Analytic Model of Maximal Experimental Value of Stress Intensity Factor K_Q for AA2519–AA1050–Ti6Al4V Layered Material

by Maciej Kotyk

Materials 2020, 13(19), 4439; https://doi.org/10.3390/ma13194439 - 6 Oct 2020

Cited by 1 | Viewed by 1769

Abstract

The article presents the results of the author’s tests involving the determination of the maximal experimental value of the stress intensity factor K_Q. This value was determined for a layered material obtained as the result of explosive welding of three alloys: [...] Read more.

The article presents the results of the author’s tests involving the determination of the maximal experimental value of the stress intensity factor K_Q. This value was determined for a layered material obtained as the result of explosive welding of three alloys: AA2519, Ti6Al4V and AA1050, and separately for each material. In both cases tests were conducted for two temperatures—the ambient temperature (293 K), and cryogenic temperature (77 K). A model for initial assessment of the K_Q value of AA2519–AA1050–Ti6Al4V (Al–Ti) layered material has also been presented. The proposed model has been developed so as to enable the determination of the curve course of load–COD for Al–Ti layered material using nominal stresses defined on the basis of a real load–COD course, obtained for the base materials, for both temperature conditions. Full article

(This article belongs to the Special Issue Investigations and Modelling of the Fracture Process in Metallic Materials)

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21 pages, 6857 KiB

Open AccessArticle

Effect of Thermal and Oxidative Aging on Asphalt Binders Rheology and Chemical Composition

by Ingrid Gabrielle do Nascimento Camargo, Bernhard Hofko, Johannes Mirwald and Hinrich Grothe

Materials 2020, 13(19), 4438; https://doi.org/10.3390/ma13194438 - 6 Oct 2020

Cited by 42 | Viewed by 3229

Abstract

Aging of asphalt binders is one of the main causes of its hardening, which negatively affects the cracking and fatigue resistance of asphalt binders. Understanding asphalt aging is crucial to improve the durability of asphalt pavements. In this regard, this study aims at [...] Read more.

Aging of asphalt binders is one of the main causes of its hardening, which negatively affects the cracking and fatigue resistance of asphalt binders. Understanding asphalt aging is crucial to improve the durability of asphalt pavements. In this regard, this study aims at understanding and differentiating the effect of temperature and oxygen uptake on the aging mechanisms of unmodified asphalt binders. For that, four laboratory aging procedures were employed. The two standardized procedures, rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), were considered to simulate the short-term and long-term aging of the asphalt binders, respectively. In addition, two thin-film aging test procedures, the nitrogen atmosphere oven aging test (NAAT) and ambient atmosphere oven aging test (OAAT) were employed to assess the effect of thermal and oxidative aging on unmodified asphalt binder properties. The NAAT procedure is based on the principle that the inert gas minimizes the oxidative aging. The rheological and chemical characterization showed that the high temperatures considered during the NAAT procedure did not change the properties of the unmodified asphalt binders. Therefore, it can be hypothesized that no significant thermal and oxidative aging was observed during NAAT aging procedure for the considered binders and that oxidative aging is the main cause for the hardening. Full article

(This article belongs to the Special Issue Novel Materials and Technologies for the Urban Roads of the Future)

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19 pages, 4884 KiB

Open AccessArticle

Laboratory Investigation of Rubberized Asphalt Using High-Content Rubber Powder

by Guoqing Wang, Xinqiang Wang, Songtao Lv, Lusheng Qin and Xinghai Peng

Materials 2020, 13(19), 4437; https://doi.org/10.3390/ma13194437 - 6 Oct 2020

Cited by 13 | Viewed by 2718

Abstract

Rubberized asphalt (RA) has been successfully applied in road engineering due to its excellent performance; however, the most widely used rubber content is about 20%.To improve the content of waste rubber and ensure its performance, seven rubberized asphalts with different powder content were [...] Read more.

Rubberized asphalt (RA) has been successfully applied in road engineering due to its excellent performance; however, the most widely used rubber content is about 20%.To improve the content of waste rubber and ensure its performance, seven rubberized asphalts with different powder content were prepared by high-speed shearing. Firstly, penetration, softening point, and ductility tests were carried out to investigate the conventional physical features of high-content rubberized asphalt (HCRA). Then, the dynamic shear rheometer test (DSR) was conducted to estimate the high-temperature rheological properties. The bending beam rheometer test (BBR) was carried out to evaluate the low-temperature rheological performance. Finally, combined with the macroscopic performance test, the modification mechanism was revealed by the Fourier transform infrared reflection (FTIR) test, and scanning electron microscope (SEM) analysis was used to observe the microscopic appearance before and after aging. The results show that rubberized asphalt has excellent properties in high- and low-temperature conditions, and fatigue resistance is also outstanding compared with neat asphalt. As the crumb rubber content increases, it is evident that the 40% RA performance is the best. The low-temperature properties of HCRA are better than the traditional 20% rubberized asphalt. This study provides a full test foundation for the efficient utilization of HCRA in road engineering. Full article

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