Materials

17 pages, 5368 KiB

Open AccessArticle

Core-shell Fe₃O₄@zeolite NaA as an Adsorbent for Cu²⁺

by Jun Cao, Peng Wang, Jie Shen and Qi Sun

Materials 2020, 13(21), 5047; https://doi.org/10.3390/ma13215047 - 10 Nov 2020

Cited by 20 | Viewed by 3855

Here, using Fe₃O₄@SiO₂ as a precursor, a novel core-shell structure magnetic Cu²⁺ adsorbent (Fe₃O₄@zeolite NaA) was successfully prepared. Several methods, namely X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), Transmission electron microscope (TEM), [...] Read more.

Here, using Fe₃O₄@SiO₂ as a precursor, a novel core-shell structure magnetic Cu²⁺ adsorbent (Fe₃O₄@zeolite NaA) was successfully prepared. Several methods, namely X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), Transmission electron microscope (TEM), Brunauer Emmett Teller (BET) and vibrating sample magnetometry (VSM) were used to characterize the adsorbent. A batch experiment was conducted to study the Cu²⁺ adsorption capacity of Fe₃O₄@zeolite NaA at different pH values, contact time, initial Cu²⁺ concentration and adsorbent does. It is found that the saturated adsorption capacity of Fe₃O₄@zeolite NaA on Cu²⁺ is 86.54 mg/g. The adsorption isotherm analysis shows that the adsorption process of Fe₃O₄@zeolite NaA to Cu²⁺ is more consistent with the Langmuir model, suggesting that it is a monolayer adsorption. Adsorption kinetics study found that the adsorption process of Fe₃O₄@zeolite NaA to Cu²⁺ follows the pseudo-second kinetics model, which means that the combination of Fe₃O₄@zeolite NaA and Cu²⁺ is the chemical chelating reaction. Thermodynamic analysis shows that the adsorption process of Fe₃O₄@zeolite NaA to Cu²⁺ is endothermic, with increasing entropy and spontaneous in nature. The above results show that Fe₃O₄@zeolite NaA is a promising Cu²⁺ adsorbent. Full article

(This article belongs to the Section Advanced Composites)

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19 pages, 4693 KiB

Open AccessArticle

On the Evolution of Temperature and Combined Stress in a Work Roll under Cyclic Thermo-Mechanical Loadings during Hot Strip Rolling and Idling

by Kejun Hu, Qinghe Shi, Wenqin Han, Fuxian Zhu and Jufang Chen

Materials 2020, 13(21), 5054; https://doi.org/10.3390/ma13215054 - 9 Nov 2020

Cited by 7 | Viewed by 2521

Abstract

An accurate prediction of temperature and stress evolution in work rolls is crucial to assess the service life of the work roll. In this paper, a finite element method (FEM) model with a deformable work roll and a meshed, rigid body considering complex [...] Read more.

An accurate prediction of temperature and stress evolution in work rolls is crucial to assess the service life of the work roll. In this paper, a finite element method (FEM) model with a deformable work roll and a meshed, rigid body considering complex thermal boundary conditions over the roll surface is proposed to assess the temperature and the thermal stress in work rolls during hot rolling and subsequent idling. After that, work rolls affected by the combined action of temperature gradient and rolling pressure are investigated by taking account of the hot strip. The accuracy of the proposed model is verified through comparison with the calculation results obtained from the mathematical model. The results show that thermal stress is dominant in the bite region of work rolls during hot rolling. Afterwards, the heat treatment residual stresses which are related to thermal fatigue are simulated and introduced into the work roll as the initial stress to evaluate the redistribution under the thermal cyclic loads during the hot rolling process. Results show that the residual stress significantly changed near the roll surface. Full article

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17 pages, 1954 KiB

Open AccessArticle

Control of Machining of Axisymmetric Low-Rigidity Parts

by Antoni Świć, Arkadiusz Gola, Łukasz Sobaszek and Olga Orynycz

Materials 2020, 13(21), 5053; https://doi.org/10.3390/ma13215053 - 9 Nov 2020

Cited by 3 | Viewed by 2084

Abstract

The specific character of the process of machining of axisymmetric low-rigidity parts makes it difficult to obtain finished products with a required accuracy of shape and dimensions and surface quality. The methods traditionally used to achieve accuracy in the machining of low-rigidity shafts [...] Read more.

The specific character of the process of machining of axisymmetric low-rigidity parts makes it difficult to obtain finished products with a required accuracy of shape and dimensions and surface quality. The methods traditionally used to achieve accuracy in the machining of low-rigidity shafts considerably reduce the efficiency of the process, fail to meet modern automation requirements, and are uneconomical and not very productive, which means new methods for controlling the machining of low-rigidity shafts need to be looked for. This article presents a structural and a calculation scheme of a machining system for the turning of low-rigidity parts and a control model based on the second-order Lagrange equation. The first section of this paper presents qualitative relationships among variables in the proposed technological system for machining axisymmetric low-rigidity parts. Moreover, schematic of the machining system for the processing of such parts as well as equations describing the energy state of the machining system is presented. Next, mathematical model of optimal system control during the machining process, which permits to control a system under specific conditions and obtains a higher shape accuracy were introduced. The key stage of the verification process concerns the numerical validation of proposed solutions. Experimental studies confirm that the utilization of the proposed mathematical models describe the properties of the original object with sufficient accuracy and allow to obtain a higher machined shaft shape accuracy. Full article

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

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10 pages, 2739 KiB

Open AccessArticle

Investigation and Possibilities of Reuse of Carbon Dioxide Absorbent Used in Anesthesiology

by Bartłomiej Rogalewicz, Agnieszka Czylkowska, Piotr Anielak and Paweł Samulkiewicz

Materials 2020, 13(21), 5052; https://doi.org/10.3390/ma13215052 - 9 Nov 2020

Cited by 4 | Viewed by 2872

Abstract

Absorbents used in closed and semi-closed circuit environments play a key role in preventing carbon dioxide poisoning. Here we present an analysis of one of the most common carbon dioxide absorbents—soda lime. In the first step, we analyzed the composition of fresh and [...] Read more.

Absorbents used in closed and semi-closed circuit environments play a key role in preventing carbon dioxide poisoning. Here we present an analysis of one of the most common carbon dioxide absorbents—soda lime. In the first step, we analyzed the composition of fresh and used samples. For this purpose, volumetric and photometric analyses were introduced. Thermal properties and decomposition patterns were also studied using thermogravimetric and X-ray powder diffraction (PXRD) analyses. We also investigated the kinetics of carbon dioxide absorption under conditions imitating a closed-circuit environment. Full article

(This article belongs to the Special Issue Thermal Analysis of Materials)

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26 pages, 4065 KiB

Open AccessArticle

Predict the Phase Angle Master Curve and Study the Viscoelastic Properties of Warm Mix Crumb Rubber-Modified Asphalt Mixture

by Fei Zhang, Lan Wang, Chao Li and Yongming Xing

Materials 2020, 13(21), 5051; https://doi.org/10.3390/ma13215051 - 9 Nov 2020

Cited by 19 | Viewed by 3161

Abstract

To identify the most accurate approach for constructing of the dynamic modulus master curves for warm mix crumb rubber modified asphalt mixtures and assess the feasibility of predicting the phase angle master curves from the dynamic modulus ones. The SM (Sigmoidal model) and [...] Read more.

To identify the most accurate approach for constructing of the dynamic modulus master curves for warm mix crumb rubber modified asphalt mixtures and assess the feasibility of predicting the phase angle master curves from the dynamic modulus ones. The SM (Sigmoidal model) and GSM (generalized sigmoidal model) were utilized to construct the dynamic modulus master curve, respectively. Subsequently, the master curve of phase angle could be predicted from the master curve of dynamic modulus in term of the K-K (Kramers–Kronig) relations. The results show that both SM and GSM can predict the dynamic modulus very well, except that the GSM shows a slightly higher correlation coefficient than SM. Therefore, it is recommended to construct the dynamic modulus master curve using GSM and obtain the corresponding phase angle master curve in term of the K-K relations. The Black space diagram and Wicket diagram were utilized to verify the predictions were consistent with the LVE (linear viscoelastic) theory. Then the master curve of storage modulus and loss modulus were also obtained. Finally, the creep compliance and relaxation modulus can be used to represent the creep and relaxation properties of warm-mix crumb rubber-modified asphalt mixtures. Full article

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

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17 pages, 14766 KiB

Open AccessArticle

Microstructure and Properties of Inconel 625 Fabricated Using Two Types of Laser Metal Deposition Methods

by Jan Dutkiewicz, Łukasz Rogal, Damian Kalita, Katarzyna Berent, Bogdan Antoszewski, Hubert Danielewski, Marek St. Węglowski, Magdalena Łazińska, Tomasz Durejko and Tomasz Czujko

Materials 2020, 13(21), 5050; https://doi.org/10.3390/ma13215050 - 9 Nov 2020

Cited by 18 | Viewed by 4164

Abstract

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO₂ laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of [...] Read more.

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO₂ laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of the Inconel 625 produced by both additive techniques was characterized using light microscopy (LM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties were characterized by tensile tests and microhardness measurements. High-power laser application resulted in a strong <100> build texture, while, at low powers, the {011} <100> Goss component increased. Both types of deposited materials showed dendritic microstructures with Ti-, Mo-, and Nb-rich zones at the cell boundaries, where numerous precipitates (Nb₂C, NbC, titanium carbides, Nb₃Ni, and NbNiCr) were also observed. It was also noted that both variants were characterized by the same slope with a proportional length, but the Inconel 625 fabricated via LENS showed a higher average yield strength (YS; 524 MPa vs. 472 MPa) and ultimate tensile strength (UTS; 944 MPa vs. 868 MPa) and lower elongation (35% vs. 42%) than samples obtained with the high-power CO₂ laser deposition process. Full article

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

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22 pages, 5484 KiB

Open AccessReview

Recent Advances in Barrier Layer of Cu Interconnects

by Zhi Li, Ye Tian, Chao Teng and Hai Cao

Materials 2020, 13(21), 5049; https://doi.org/10.3390/ma13215049 - 9 Nov 2020

Cited by 77 | Viewed by 10105

Abstract

The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum [...] Read more.

The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum nitride (Ta/TaN) has been widely used as an inter-layer to separate the dielectric layer and the Cu. However, to fulfill the demand for continuous down-scaling of the Cu technology node, traditional materials and technical processes are being challenged. Direct electrochemical deposition of Cu on top of Ta/TaN is not realistic, due to its high resistivity. Therefore, pre-deposition of a Cu seed layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD) is necessary, but the non-uniformity of the Cu seed layer has a devastating effect on the defect-free fill of modern sub-20 or even sub-10 nm Cu technology nodes. New Cu diffusion barrier materials having ultra-thin size, high resistivity and stability are needed for the successful super-fill of trenches at the nanometer scale. In this review, we briefly summarize recent advances in the development of Cu diffusion-proof materials, including metals, metal alloys, self-assembled molecular layers (SAMs), two-dimensional (2D) materials and high-entropy alloys (HEAs). Also, challenges are highlighted and future research directions are suggested. Full article

(This article belongs to the Special Issue Interfacial and Transport Phenomena between Liquid Metal and Solid Structural Materials)

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9 pages, 2606 KiB

Open AccessArticle

Statistical Research of Stainless Austenitic Steel Grain Size Distribution after Screw Rolling

by Mikhail Mikhailovich Skripalenko, Tatyana Viktorovna Zavyalova, Zbigniew Pater, Boris Alekseevich Romantsev, Stanislav Olegovich Rogachev, Liudmila Mikhailovna Kaputkina, Mikhail Nikolaevich Skripalenko and Andrei Vladimirovich Danilin

Materials 2020, 13(21), 5048; https://doi.org/10.3390/ma13215048 - 9 Nov 2020

Cited by 5 | Viewed by 1719

Abstract

Screw rolling of austenitic stainless-steel billets was conducted in two- and three-high mills. Statistical research results showed that, compared to heated but not rolled conditions, both screw rolling techniques provided a decrease of grain size, variance, grain size distribution asymmetry, and excess in [...] Read more.

Screw rolling of austenitic stainless-steel billets was conducted in two- and three-high mills. Statistical research results showed that, compared to heated but not rolled conditions, both screw rolling techniques provided a decrease of grain size, variance, grain size distribution asymmetry, and excess in the billet cross-section at the stationary stage of screw rolling. At that stage, grain size distribution after two-high screw rolling is closer to normal in terms of asymmetry and excess values compared to grain-size distribution after three-high screw rolling. A strong negative correlation between strain effective values and grain-size values for the cross-section of the rolled billets at the stationary stage was revealed for both two- and three-high screw rolling. Full article

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17 pages, 10805 KiB

Open AccessEditor’s ChoiceArticle

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

by Xueyong Zhou, Yuan Jin and Jianke Du

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

Cited by 40 | Viewed by 4501

Abstract

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

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

(This article belongs to the Section Porous Materials)

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17 pages, 5317 KiB

Open AccessEditor’s ChoiceArticle

Equivalent Cement Clinker Obtained by Indirect Mechanosynthesis Process

by Rabah Hamzaoui and Othmane Bouchenafa

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

Cited by 8 | Viewed by 2437

Abstract

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

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

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

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14 pages, 6067 KiB

Open AccessArticle

Thermo-Optical Switching Effect Based on a Tapered Optical Fiber and Higher Alkanes Doped with ZnS:Mn

by Joanna E. Moś, Karol A. Stasiewicz, Katarzyna Matras-Postołek and Leszek R. Jaroszewicz

Materials 2020, 13(21), 5044; https://doi.org/10.3390/ma13215044 - 9 Nov 2020

Cited by 5 | Viewed by 2615

Abstract

The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by [...] Read more.

The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550–1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor. Full article

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

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12 pages, 4238 KiB

Open AccessArticle

Crystallization Kinetics of Modified Basalt Glass

by Yonglin Huo, Guilu Qin, Jichuan Huo, Xingquan Zhang, Baogang Guo, Kaijun Zhang, Jun Li, Ming Kang and Yanhui Zou

Materials 2020, 13(21), 5043; https://doi.org/10.3390/ma13215043 - 9 Nov 2020

Cited by 8 | Viewed by 2228

Abstract

As the raw material for the production of basalt continuous fibers in Sichuan, basalt glass (BG) and modified basalt glass (MBG) were prepared by the melt quenching method with the basalt and chemically modified basalt, respectively. The crystallization kinetics of BG and MBG [...] Read more.

As the raw material for the production of basalt continuous fibers in Sichuan, basalt glass (BG) and modified basalt glass (MBG) were prepared by the melt quenching method with the basalt and chemically modified basalt, respectively. The crystallization kinetics of BG and MBG were investigated by differential scanning calorimetry (DSC) according to Kissinger methods. The results revealed that it is difficult for both glasses to crystallize at a high temperature. In addition, the crystallization activation energy of MBG is much higher than that of BG, which indicates that MBG is more difficult to crystallize than BG. The crystalline phases seemed to be formed from the surface of the two glasses. The morphologies and crystal structure of the crystalline phases in the heat-treated BG and MBG were analyzed by scanning electron microscope (SEM/EDX) and XRD. It was found that only a small amount of crystalline phase can be observed in the MBG, which indicates that the crystallization ability of the MBG was greatly suppressed. Results of this initial investigation indicate that chemical modification can effectively suppress the crystallization tendency of basalt glass and improve its thermal stability, which opens up an effective way for the industrial scale and stable production of basalt fiber. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 3223 KiB

Open AccessArticle

Mimicking the Mechanical Properties of Aortic Tissue with Pattern-Embedded 3D Printing for a Realistic Phantom

by Jaeyoung Kwon, Junhyeok Ock and Namkug Kim

Materials 2020, 13(21), 5042; https://doi.org/10.3390/ma13215042 - 9 Nov 2020

Cited by 16 | Viewed by 3861

Abstract

3D printing technology has been extensively applied in the medical field, but the ability to replicate tissues that experience significant loads and undergo substantial deformation, such as the aorta, remains elusive. Therefore, this study proposed a method to imitate the mechanical characteristics of [...] Read more.

3D printing technology has been extensively applied in the medical field, but the ability to replicate tissues that experience significant loads and undergo substantial deformation, such as the aorta, remains elusive. Therefore, this study proposed a method to imitate the mechanical characteristics of the aortic wall by 3D printing embedded patterns and combining two materials with different physical properties. First, we determined the mechanical properties of the selected base materials (Agilus and Dragonskin 30) and pattern materials (VeroCyan and TPU 95A) and performed tensile testing. Three patterns were designed and embedded in printed Agilus–VeroCyan and Dragonskin 30–TPU 95A specimens. Tensile tests were then performed on the printed specimens, and the stress-strain curves were evaluated. The samples with one of the two tested orthotropic patterns exceeded the tensile strength and strain properties of a human aorta. Specifically, a tensile strength of 2.15 ± 0.15 MPa and strain at breaking of 3.18 ± 0.05 mm/mm were measured in the study; the human aorta is considered to have tensile strength and strain at breaking of 2.0–3.0 MPa and 2.0–2.3 mm/mm, respectively. These findings indicate the potential for developing more representative aortic phantoms based on the approach in this study. Full article

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11 pages, 2782 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 7 | Viewed by 3131

Abstract

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

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

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

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11 pages, 2807 KiB

Open AccessArticle

Effects of Copper Metallic Nanoparticles on Structural and Optical Properties of Antimony Phosphate Glasses Co-Doped with Samarium Ions

by Petru Pascuta, Razvan Stefan, Loredana Elena Olar, Liviu Calin Bolundut and Eugen Culea

Materials 2020, 13(21), 5040; https://doi.org/10.3390/ma13215040 - 9 Nov 2020

Cited by 9 | Viewed by 2487

Abstract

New antimony phosphate glasses doped with samarium (III) oxide and co-doped with copper metallic nanoparticles (CuNPs) were obtained by the melt quenching technique. The samples were analyzed by X-ray diffraction analysis (XRD), electron paramagnetic resonance (EPR), ultraviolet-visible (UV–Vis) and photoluminescence (PL) spectroscopies. XRD [...] Read more.

New antimony phosphate glasses doped with samarium (III) oxide and co-doped with copper metallic nanoparticles (CuNPs) were obtained by the melt quenching technique. The samples were analyzed by X-ray diffraction analysis (XRD), electron paramagnetic resonance (EPR), ultraviolet-visible (UV–Vis) and photoluminescence (PL) spectroscopies. XRD data suggested that all the obtained samples showed an amorphous nature. EPR data suggested the existence of Cu²⁺ ions octahedrally surrounded by six oxygen atoms. The dipole–dipole interactions between Cu²⁺ ions were predominant. UV–Vis spectra revealed the presence of Sm³⁺ and Cu²⁺ ions in the samples. The values for nephelauxetic and bonding parameters were also calculated. The negative values obtained for bonding parameter indicate an ionic character of the bonds from the glass network. Photoluminescence spectra exhibited emissions from samarium ions and revealed the influence of dopant nature on of rare-earth ions emissions. The obtained results indicate that the studied materials are suitable for solid state lasers. Full article

(This article belongs to the Special Issue Optical and Magnetic Properties of Glass and Glass Ceramics)

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15 pages, 17491 KiB

Open AccessArticle

Investigation of the Effect of Inhomogeneous Material on the Fracture Mechanisms of Bamboo by Finite Element Method

by Raviduth Ramful and Atsushi Sakuma

Materials 2020, 13(21), 5039; https://doi.org/10.3390/ma13215039 - 9 Nov 2020

Cited by 12 | Viewed by 2992

Abstract

Bamboo is a remarkably strong and sustainable material available for construction. It exhibits optimized mechanical characteristics based on a hollow-inhomogeneous structure which also affects its fracture behavior. In this study, the aim is to investigate the effect of material composition and geometrical attributes [...] Read more.

Bamboo is a remarkably strong and sustainable material available for construction. It exhibits optimized mechanical characteristics based on a hollow-inhomogeneous structure which also affects its fracture behavior. In this study, the aim is to investigate the effect of material composition and geometrical attributes on the fracture mechanisms of bamboo in various modes of loading by the finite element method. In the first part of the investigation, the optimized transverse isotropy of bamboo to resist transverse deformation was numerically determined to represent its noticeable orthotropic characteristics which prevail in the axial direction. In the second part of this study, a numerical investigation of fracture mechanisms in four fundamental modes of loading, namely bending, compression, torsion, and shear, were conducted by considering the failure criterion of maximum principal strain. A crack initiation stage was simulated and compared by implementing an element erosion technique. Results showed that the characteristics of bamboo’s crack initiation differed greatly from solid geometry and homogeneous material-type models. Splitting patterns, which were discerned in bending and shear modes, differed in terms of location and occurred in the outside-center position and inside-lowermost position of the culm, respectively. The results of this study can be useful in order to achieve optimized strength in bamboo-inspired bionic designs. Full article

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

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16 pages, 8415 KiB

Open AccessArticle

Chitosan-Based Thermo-Sensitive Hydrogel Loading Oyster Peptides for Hemostasis Application

by Dongying Zhang, Zhang Hu, Lingyu Zhang, Sitong Lu, Fengyan Liang and Sidong Li

Materials 2020, 13(21), 5038; https://doi.org/10.3390/ma13215038 - 9 Nov 2020

Cited by 38 | Viewed by 4044

Abstract

Uncontrolled massive hemorrhage is one of the principal causes of death in trauma emergencies. By using catechol-modified chitosan (CS-C) as the matrix material and β glycerol phosphate (β-GP) as a thermo-sensitive agent, chitosan-based thermo-sensitive hydrogel loading oyster peptides (CS-C/OP/β-GP) were prepared at physiological [...] Read more.

Uncontrolled massive hemorrhage is one of the principal causes of death in trauma emergencies. By using catechol-modified chitosan (CS-C) as the matrix material and β glycerol phosphate (β-GP) as a thermo-sensitive agent, chitosan-based thermo-sensitive hydrogel loading oyster peptides (CS-C/OP/β-GP) were prepared at physiological temperature. The hemostatic performance of CS-C/OP/β-GP hydrogel was tested in vivo and in vitro, and its biological safety was evaluated. The results showed that the in vitro coagulation time and blood coagulation index of CS-C/OP/β-GP hydrogel were better than those of a commercial gelatin sponge. Notably, compared with the gelatin sponge, CS-C/OP/β-GP hydrogel showed that the platelet adhesion and erythrocyte adsorption rates were 38.98% and 95.87% higher, respectively. Additionally, the hemostasis time in mouse liver injury was shortened by 19.5%, and the mass of blood loss in the mouse tail amputation model was reduced by 18.9%. The safety evaluation results demonstrated that CS-C/OP/β-GP had no cytotoxicity to L929 cells, and the hemolysis rates were less than 5% within 1 mg/mL, suggesting good biocompatibility. In conclusion, our results indicate that CS-C/OP/β-GP is expected to be a promising dressing in the field of medical hemostasis. Full article

(This article belongs to the Special Issue Advanced Biomaterials for Medical Applications)

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15 pages, 4072 KiB

Open AccessEditor’s ChoiceArticle

Characteristics of Interfacial Shear Bonding Between Basalt Fiber and Mortar Matrix

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

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

Cited by 6 | Viewed by 2290

Abstract

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

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

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

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15 pages, 7079 KiB

Open AccessArticle

Effect of a Boric Acid Corrosive Environment on the Microstructure and Properties of Concrete

by Yu Wang, Bei Huang, Zhongyang Mao, Min Deng and Huan Cao

Materials 2020, 13(21), 5036; https://doi.org/10.3390/ma13215036 - 8 Nov 2020

Cited by 8 | Viewed by 3219

Abstract

Boric acid, a weak acid, is often used to shield neutrons in water cooling systems in nuclear power stations. The leakage of boric acid in water cooling systems damages the concrete structure and affects the safety of nuclear power engineering. In this experiment, [...] Read more.

Boric acid, a weak acid, is often used to shield neutrons in water cooling systems in nuclear power stations. The leakage of boric acid in water cooling systems damages the concrete structure and affects the safety of nuclear power engineering. In this experiment, concrete specimens were cured with boric acid at 20, 40, and 70 °C to study the effect of boric acid on the microstructure and properties of concrete. X-ray diffraction (XRD) and thermogravimetry and differential scanning calorimetry (TG-DSC) were used to analyze the change in mineral composition. The microstructure was examined by scanning electron microscope (SEM). The porosity of the concrete was examined by mercury intrusion porosimetry (MIP). The results show that the performance of specimens was stable under the curing conditions of 20 and 40 °C. Under the curing environment of 70 °C, the performance of concrete cured with 0, 2000, and 7000 ppm concentrations was stable, but the compressive strength of the 180,000 ppm specimen was reduced by 27.8% and suffered the most serious loss of mass and surface corrosion, with the most harmful pores. The high concentration of boric acid seriously damaged the surface structure of concrete, which is the main reason for its loss of properties. This situation is extremely dangerous in nuclear power engineering, so the effect of boric acid leakage cannot be ignored. Full article

(This article belongs to the Special Issue Corrosion Behaviour in Concrete)

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13 pages, 1330 KiB

Open AccessArticle

A Novel, Nontoxic and Scalable Process to Produce Lipidic Vehicles

by Nikolaos Naziris, Natassa Pippa and Costas Demetzos

Materials 2020, 13(21), 5035; https://doi.org/10.3390/ma13215035 - 8 Nov 2020

Cited by 8 | Viewed by 2232

Abstract

Lipidic vehicles are novel industrial products, utilized as components for pharmaceutical, cosmeceutical and nutraceutical formulations. The present study concerns a newly invented method to produce lipidic vehicles in the nanoscale that is simple, nontoxic, versatile, time-efficient, low-cost and easy to scale up. The [...] Read more.

Lipidic vehicles are novel industrial products, utilized as components for pharmaceutical, cosmeceutical and nutraceutical formulations. The present study concerns a newly invented method to produce lipidic vehicles in the nanoscale that is simple, nontoxic, versatile, time-efficient, low-cost and easy to scale up. The process is a modification of the heating method (MHM) and comprises (i) providing a mixture of an amphiphilic lipid and a charged lipid and/or a fluidity regulator in a liquid medium composed of water and a liquid polyol, (ii) stirring and heating the mixture in two heating steps, wherein the temperature of the second step is higher than the temperature of the first step and (iii) allowing the mixture to cool down to room temperature. The process leads to the self-assembly of nanoparticles of small size and good homogeneity, compared with conventional approaches that require additional size reduction steps. In addition, the incorporation of bioactive molecules, such as drugs, inside the nanoparticles is possible, while lyophilization of the products provides long-term stability. Most importantly, the absence of toxic solvents and the simplicity guarantee the safety and scalability of the process, distinguishing it from most prior art processes to produce lipidic vehicles. Full article

(This article belongs to the Special Issue Drug Delivery: Recent Developments and Future Prospects)

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19 pages, 4289 KiB

Open AccessArticle

Iron Oxide/Phosphatic Materials Composites with Potential Applications in Environmental Protection

by Georgiana Cornelia Ispas, Raluca Manea, Roxana Ioana Brazdis, Anda Maria Baroi, Toma Fistos, Radu Claudiu Fierascu and Monica Florentina Raduly

Materials 2020, 13(21), 5034; https://doi.org/10.3390/ma13215034 - 8 Nov 2020

Cited by 5 | Viewed by 3136

Abstract

Currently, hydroxyapatite is probably the most researched material, due to its multiple applications in medical, environmental, or cultural heritage, when the classical structure is modified and calcium is displaced partially or totally with different metals. By changing the classical structure of the hydroxyapatite, [...] Read more.

Currently, hydroxyapatite is probably the most researched material, due to its multiple applications in medical, environmental, or cultural heritage, when the classical structure is modified and calcium is displaced partially or totally with different metals. By changing the classical structure of the hydroxyapatite, new morphologies can be obtained, thus allowing final applications different from those of the initial hydroxyapatite material. However, their properties should be tuned for the desired application. In this context, the present paper describes the synthesis and characterization (through energy-dispersive X-ray fluorescence, X-ray diffraction, FTIR, thermal analysis, and transmission electron microscopy) of iron oxide/manganese-containing phosphatic phase composite materials, developed in order to obtain the enhancement of final environmental applications (photodegradation of dyes, adsorption of organic compounds). The composite material was tested for photocatalytic properties, after embedding in hydrosoluble film-forming materials. Photocatalytic coatings show different activity during the photodecomposition of Methylene Blue, used as a model of a contaminant. The photocatalytic activities of the materials were discussed in relationship with both the phosphatic materials and the magnetic components. Finally, other environmental applications were studied for the developed materials (adsorption of non-steroidal anti-inflammatory drugs—paracetamol and ibuprofen), revealing an enhancement of the adsorption capacity of the phosphatic material upon addition of the magnetic phase. Full article

(This article belongs to the Special Issue Nano-Composite Coatings: Processing, Characterization, Properties, and Applications)

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15 pages, 3259 KiB

Open AccessArticle

Reasons for the Formation of Non-Fibrous Inclusions When Preparing Basalt Fibers by the Duplex Method

by Anri Elbakian, Milan Sága, Boris Sentyakov, Ivan Kuric and Peter Kopas

Materials 2020, 13(21), 5033; https://doi.org/10.3390/ma13215033 - 8 Nov 2020

Cited by 2 | Viewed by 1636

Abstract

Materials based on basalt fiber are widely used as thermal insulating material. These materials have a number of advantages, including their low thermal conductivity and fire resistance due to their natural composition. However, there is a significant drawback in that the material contain [...] Read more.

Materials based on basalt fiber are widely used as thermal insulating material. These materials have a number of advantages, including their low thermal conductivity and fire resistance due to their natural composition. However, there is a significant drawback in that the material contain non-fibrous inclusions. The solution to this problem would significantly improve the working conditions of workers engaged in the production of materials from basalt fiber, as well as workers engaged in construction and installation works. In addition, the research will help to make completely new products, such as special fireproof paper and sterile medical materials. This article focuses on the reasons for the formation of non-fibrous inclusions in the production of this kind of material. The technology of producing canvases from superthin fiber in the duplex way is studied. The analysis of the production process is made. Certain technological and structural parameters of the influence on the formation of such inclusions are identified. Experiments are carried out and conclusions are drawn given formation of non-fibrous inclusions of various geometric shapes for various factors. A mathematical model of the process under consideration is built. The article draws conclusion on the application of these developments in the production cycle of creating materials based on basalt fiber. Full article

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25 pages, 7534 KiB

Open AccessArticle

Study of the Rolling Friction Coefficient between Dissimilar Materials through the Motion of a Conical Pendulum

by Stelian Alaci, Ilie Muscă and Ștefan-Gheorghe Pentiuc

Materials 2020, 13(21), 5032; https://doi.org/10.3390/ma13215032 - 8 Nov 2020

Cited by 9 | Viewed by 3344

Abstract

The rolling friction phenomenon is encountered in a wide range of applications and when two different materials are involved, quantitative characterization is necessary. The parameter to be determined is the coefficient of rolling friction, for whose estimation a methodology is proposed, based on [...] Read more.

The rolling friction phenomenon is encountered in a wide range of applications and when two different materials are involved, quantitative characterization is necessary. The parameter to be determined is the coefficient of rolling friction, for whose estimation a methodology is proposed, based on the damped oscillation of a conical pendulum. The pure rolling contact between a sphere and a plane is obtained when a steel ball is the bob of the pendulum, which rolls on an inclined plate made from a second material from the contacting pair. The mathematical model of the motion of a conical pendulum constructed from a revolution body supported on an inclined plane in the presence of the rolling friction is developed. The dynamic equations of the rigid body with fixed point are applied and the differential equation of motion of the pendulum is obtained together with the expressions of the reaction forces in the contact point. For different pairs of materials, tests are performed on a laboratory device. The damped oscillatory motion of the conical pendulum is video-captured for the estimation of the angular amplitude variation. A program for image processing is developed for measuring the values of angular elongations from the analysis of each frame of the video and, finally, the coefficient of rolling friction is obtained. For all the materials tested, a linear decrease in angular amplitude is detected and the slope of angular amplitude can be considered as a characteristic parameter related to the coefficient of rolling friction between the two materials. Full article

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16 pages, 4837 KiB

Open AccessArticle

Adsorption of Chiral [5]-Aza[5]helicenes on DNA Can Modify Its Hydrophilicity and Affect Its Chiral Architecture: A Molecular Dynamics Study

by Giuseppina Raffaini, Andrea Mele and Tullio Caronna

Materials 2020, 13(21), 5031; https://doi.org/10.3390/ma13215031 - 7 Nov 2020

Cited by 5 | Viewed by 3189

Abstract

Helicenes are interesting chiral molecules without asymmetric carbon atoms but with intrinsic chirality. Functionalized 5-Aza[5]helicenes can form non-covalent complexes with anticancer drugs and therefore be potential carriers. The paper highlights the different structural selectivity for DNA binding for two enantiopure compounds and the [...] Read more.

Helicenes are interesting chiral molecules without asymmetric carbon atoms but with intrinsic chirality. Functionalized 5-Aza[5]helicenes can form non-covalent complexes with anticancer drugs and therefore be potential carriers. The paper highlights the different structural selectivity for DNA binding for two enantiopure compounds and the influence of concentration on their adsorption and self-aggregation process. In this theoretical study based on atomistic molecular dynamics simulations the interaction between (M)- and (P)-5-Aza[5]helicenes with double helix B-DNA is investigated. At first the interaction of single pure enantiomer with DNA is studied, in order to find the preferred site of interaction at the major or minor groove. Afterwards, the interaction of the enantiomers at different concentrations was investigated considering both competitive adsorption on DNA and possible helicenes self-aggregation. Therefore, racemic mixtures were studied. The helicenes studied are able to bind DNA modulating or locally modifying its hydrophilic surface into hydrophobic after adsorption of the first helicene layer partially covering the negative charge of DNA at high concentration. The (P)-enantiomer shows a preferential binding affinity of DNA helical structure even during competitive adsorption in the racemic mixtures. These DNA/helicenes non-covalent complexes exhibit a more hydrophobic exposed surface and after self-aggregation a partially hidden DNA chiral architecture to the biological environment. Full article

(This article belongs to the Special Issue Chiral Materials)

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20 pages, 5825 KiB

Open AccessArticle

The Study of Structural, Impedance and Energy Storage Behavior of Plasticized PVA:MC Based Proton Conducting Polymer Blend Electrolytes

by Shujahadeen B. Aziz, Iver Brevik, M. A. Brza, A. S. F. M. Asnawi, Elham M. A. Dannoun, Y. M. Yusof, Rebar T. Abdulwahid, M. H. Hamsan, Muaffaq M. Nofal and M. F. Z. Kadir

Materials 2020, 13(21), 5030; https://doi.org/10.3390/ma13215030 - 7 Nov 2020

Cited by 11 | Viewed by 3180

Abstract

In this study, structural characterization, electrical properties and energy storage performance of plasticized polymer electrolytes based on polyvinyl alcohol/methylcellulose/ammonium thiocyanate (PVA/MC-NH₄SCN) were carried out. An X-ray diffraction (XRD) study displayed that the plasticized electrolyte system with the uppermost value of direct [...] Read more.

In this study, structural characterization, electrical properties and energy storage performance of plasticized polymer electrolytes based on polyvinyl alcohol/methylcellulose/ammonium thiocyanate (PVA/MC-NH₄SCN) were carried out. An X-ray diffraction (XRD) study displayed that the plasticized electrolyte system with the uppermost value of direct current (DC) ionic conductivity was the most amorphous system. The electrolyte in the present work realized an ionic conductivity of 2.903 × 10⁻³ Scm⁻¹ at room temperature. The main charge carrier in the electrolyte was found to be the ions with the ionic transference number (t_ion) of 0.912, compared to only 0.088 for the electronic transference number (t_elec). The electrochemical stability potential window of the electrolyte is 2.1 V. The specific capacitance was found to reduce from 102.88 F/g to 28.58 F/g as the scan rate increased in cyclic voltammetry (CV) analysis. The fabricated electrochemical double layer capacitor (EDLC) was stable up to 200 cycles with high efficiency. The specific capacitance obtained for the EDLC by using charge–discharge analysis was 132.7 F/g at the first cycle, which is slightly higher compared to the CV plot. The equivalent series resistance (ESR) increased from 58 to 171

Ω

throughout the cycles, which indicates a good electrolyte/electrode contact. Ions in the electrolyte were considered to have almost the same amount of energy during the conduction process as the energy density is approximately at 14.0 Wh/kg throughout the 200 cycles. The power density is stabilized at the range of 1444.3 to 467.6 W/kg as the EDLC completed the cycles. Full article

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

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30 pages, 41082 KiB

Open AccessArticle

Non-Destructive Testing Mechanism for Pre-Stressed Steel Wire Using Acoustic Emission Monitoring

by Jothi Saravanan Thiyagarajan

Materials 2020, 13(21), 5029; https://doi.org/10.3390/ma13215029 - 7 Nov 2020

Cited by 10 | Viewed by 2870

Abstract

In this paper, the guided ultrasonic wave propagation characteristics in the axisymmetric pre-stressed viscoelastic waveguide for acoustic emission (AE) monitoring, using the semi-analytical finite element (SAFE) method, is studied broadly. For the numerical investigation, a single high-strength steel wire is considered. A comprehensive [...] Read more.

In this paper, the guided ultrasonic wave propagation characteristics in the axisymmetric pre-stressed viscoelastic waveguide for acoustic emission (AE) monitoring, using the semi-analytical finite element (SAFE) method, is studied broadly. For the numerical investigation, a single high-strength steel wire is considered. A comprehensive and in-depth study on the AE signal’s propagation characteristics is carried out based on the SAFE method. Both undamped and damped waveguides are considered for attaining SAFE solutions and presented in a detailed manner. The SAFE method for an axisymmetric cross-section in cylindrical coordinates analyzes the two main influencing factors of steel wire in a practical scenario: Material damping and initial tension. For the effect of initial stress, the calculation shows that the initial tensile stress can increase and decrease the energy velocity and attenuation factor of most modal waves above the cut-off frequency, and the effect is linear. Some longitudinal wave modes in the high-frequency region show their potential for AE monitoring as these modes have a low attenuation factor and small external surface vibration. By considering various states of initial stress in a damped waveguide, the effect of pre-stress on the dispersion characteristics is understood in a better manner. A non-destructive testing (NDT) mechanism for pre-stressed steel wire using AE monitoring is proposed for the health monitoring of structures. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)

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16 pages, 8146 KiB

Open AccessArticle

Mechanical Properties of High-Strength Cu–Cr–Zr Alloy Fabricated by Selective Laser Melting

by Fujia Sun, Ping Liu, Xiaohong Chen, Honglei Zhou, Pengfei Guan and Bilan Zhu

Materials 2020, 13(21), 5028; https://doi.org/10.3390/ma13215028 - 7 Nov 2020

Cited by 32 | Viewed by 3749

Abstract

The approximate process range for preparing the Cu–Cr–Zr alloy by selective laser melting (SLM) was determined by ANSYS simulation, and the influence of the SLM process parameters on the comprehensive properties of the SLM-formed alloy was studied by the design of experiments. The [...] Read more.

The approximate process range for preparing the Cu–Cr–Zr alloy by selective laser melting (SLM) was determined by ANSYS simulation, and the influence of the SLM process parameters on the comprehensive properties of the SLM-formed alloy was studied by the design of experiments. The Cu–Cr–Zr alloy with optimum strength and hardness was prepared with high efficiency by optimizing the process parameters for SLM (i.e., laser power, scanning speed, and hatching distance). It is experimentally shown that tensile strength and hardness of the SLM alloy are increased by increasing laser power and decreasing scanning speed, whereas they are initially increased and then decreased by increasing the hatching distance. Moreover, strength, roughness and hardness of the SLM alloy are optimized when laser power is 460 W, scanning speed is 700 mm/s and hatching distance is 0.06 mm. The optimized properties of the SLM alloy are a tensile strength of 153.5 MPa, hardness of 119 HV, roughness of 31.384 μm and relative density of 91.62%. Full article

(This article belongs to the Section Electronic Materials)

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14 pages, 8068 KiB

Open AccessArticle

The Influence of Ball Burnishing on Friction in Lubricated Sliding

by Slawomir Swirad and Pawel Pawlus

Materials 2020, 13(21), 5027; https://doi.org/10.3390/ma13215027 - 7 Nov 2020

Cited by 10 | Viewed by 2408

Abstract

Ball burnishing treatment, using the Ecoroll system, of steel samples was conducted. In the experiment, the burnishing pressure was changed. After the treatments, measurements of the surface topographies of disc samples were conducted using a white light interferometer Talysurf CCI Lite. Tribological tests [...] Read more.

Ball burnishing treatment, using the Ecoroll system, of steel samples was conducted. In the experiment, the burnishing pressure was changed. After the treatments, measurements of the surface topographies of disc samples were conducted using a white light interferometer Talysurf CCI Lite. Tribological tests were carried out in a ball-on-disc configuration. After these tests, measurements of surface topographies of disc samples were repeated. Worn surfaces were also analyzed with a scanning electron microscope. It was found that as the result of burnishing, surface topography height of tested samples decreased. Ball burnishing led to a reduction in the frictional resistance. The highest friction reduction of more than 40% was achieved with a burnishing pressure of 20 MPa. Full article

(This article belongs to the Special Issue Tribology: Friction and Wear of Engineering Materials)

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19 pages, 3104 KiB

Open AccessArticle

Comparison of Contemporary Elm (Ulmus spp.) and Degraded Archaeological Elm: The Use of Dynamic Mechanical Analysis Under Ambient Moisture Conditions

by Morwenna J. Spear and Magdalena Broda

Materials 2020, 13(21), 5026; https://doi.org/10.3390/ma13215026 - 7 Nov 2020

Cited by 12 | Viewed by 2485

Abstract

This paper describes dynamic mechanical analysis (DMA) experiments on archaeological and contemporary elm tested under air-dry conditions, to explore the suitability of this technique for increasing understanding of the viscoelastic behaviour of archaeological wood. A strong reduction of storage modulus of archaeological elm [...] Read more.

This paper describes dynamic mechanical analysis (DMA) experiments on archaeological and contemporary elm tested under air-dry conditions, to explore the suitability of this technique for increasing understanding of the viscoelastic behaviour of archaeological wood. A strong reduction of storage modulus of archaeological elm (AE) was seen in comparison with contemporary wood (CE), resulting from the high degree of wood degradation, notably the reduction in hemicelluloses and cellulose content of AE, as demonstrated by Attenuated Total Reflection–Fourier Transform Infra-Red spectroscopy (ATR-FTIR). The γ relaxation peak was observed in all samples. The γ peak in AE shifted to a higher temperature, and the activation energy for γ-peak motions was lower in AE (29 kJ/mol) than in CE (50 kJ/mol) indicating that motion is less restricted within the degraded AE cell wall, or possibly a difference in the monomer undergoing rotation. Detection of changes in storage modulus are well known, but the DMA temperature scan technique proved to be useful for probing the degree of wood degradation, relating to the changes in location and intensity of secondary relaxation peaks. The γ peak in loss factor can be used to confirm that cell wall degradation is at an advanced stage, and to improve understanding of the internal spatial structure of the degraded wood cell wall. Full article

(This article belongs to the Section Materials Physics)

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20 pages, 8411 KiB

Open AccessArticle

Investigations of Liquid Steel Viscosity and Its Impact as the Initial Parameter on Modeling of the Steel Flow through the Tundish

by Marta Ślęzak and Marek Warzecha

Materials 2020, 13(21), 5025; https://doi.org/10.3390/ma13215025 - 7 Nov 2020

Cited by 4 | Viewed by 3172

Abstract

The paper presents research carried out to experimentally determine the dynamic viscosity of selected iron solutions. A high temperature rheometer with an air bearing was used for the tests, and ANSYS Fluent commercial software was used for numerical simulations. The experimental results obtained [...] Read more.

The paper presents research carried out to experimentally determine the dynamic viscosity of selected iron solutions. A high temperature rheometer with an air bearing was used for the tests, and ANSYS Fluent commercial software was used for numerical simulations. The experimental results obtained are, on average, lower by half than the values of the dynamic viscosity coefficient of liquid steel adopted during fluid flow modeling. Numerical simulations were carried out, taking into account the viscosity standard adopted for most numerical calculations and the average value of the obtained experimental dynamic viscosity of the analyzed iron solutions. Both qualitative and quantitative analysis showed differences in the flow structure of liquid steel in the tundish, in particular in the predicted values and the velocity profile distribution. However, these differences are not significant. In addition, the work analyzed two different rheological models—including one of our own—to describe the dynamic viscosity of liquid steel, so that in the future, the experimental stage could be replaced by calculating the value of the dynamic viscosity coefficient of liquid steel using one equation. The results obtained support the use of the author’s rheological model for the above; however, this model still needs to be refined and extended to a wide range of alloying elements, mainly the extension of the carbon range. Full article

(This article belongs to the Special Issue Research on Machining Methods and Mechanical Properties of Alloys)

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