Materials

13 pages, 2570 KiB

Open AccessArticle

The Influence of Plasma Treatment on the Corrosion and Biocompatibility of Magnesium

by Aleksandra Kocijan, Janez Kovač, Ita Junkar, Matic Resnik, Veno Kononenko and Marjetka Conradi

Materials 2022, 15(20), 7405; https://doi.org/10.3390/ma15207405 - 21 Oct 2022

Cited by 2 | Viewed by 1266

Abstract

In our study, plasma surface modification was employed to tailor the surface properties of magnesium in terms of surface chemistry, topography, and wettability. For two sets of samples, the plasma treatment involved two steps using two different gases (hydrogen and oxygen), while one [...] Read more.

In our study, plasma surface modification was employed to tailor the surface properties of magnesium in terms of surface chemistry, topography, and wettability. For two sets of samples, the plasma treatment involved two steps using two different gases (hydrogen and oxygen), while one set of samples was treated with one step only using oxygen. X-ray photoelectron spectroscopy (XPS) was applied to determine the surface composition, oxidation state of the elements, and the thickness of the surface oxide layer on the Mg samples after different plasma treatments. The surface morphology was characterised using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The wettability was analysed by measuring the static water-contact angles and the corrosion was evaluated using potentiodynamic measurements. The interaction of the live cells with the differently modified Mg surfaces was evaluated in terms of biocompatibility using MG-63 cells (human bone osteosarcoma cells). We have shown that a plasma surface treatment significantly decreased the carbon content and the formation of a 15–20-nm-thick MgO layer was observed. This improves the corrosion resistance, while the biocompatibility was retained, compared to the untreated Mg. A plasma surface treatment is therefore an important step in the development of novel surfaces with improved corrosion resistance for magnesium in biomedical applications. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Metallic Materials II)

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23 pages, 13635 KiB

Open AccessArticle

Research on the Behavior of Stiffening Walls in Single-Storey Buildings Made of Autoclaved Aerated Concrete (AAC) Masonry Units

by Krzysztof Grzyb and Radosław Jasiński

Materials 2022, 15(20), 7404; https://doi.org/10.3390/ma15207404 - 21 Oct 2022

Cited by 4 | Viewed by 1665

Abstract

Experimental identification of stiffening walls is often limited to studying single-wall models. However, these samples do not reflect many additional effects—torsion of the building and redistribution of internal forces. This paper presents the results of two full-scale buildings made of autoclaved aerated concrete [...] Read more.

Experimental identification of stiffening walls is often limited to studying single-wall models. However, these samples do not reflect many additional effects—torsion of the building and redistribution of internal forces. This paper presents the results of two full-scale buildings made of autoclaved aerated concrete (AAC) masonry elements. The primary purpose of the work was to determine the changes in the stiffness of the shear walls and to attempt the empirical distribution of loads on the stiffening walls. The intermediate goals were: a description of the crack morphology and the mechanism of failure, the designation of the stiffening walls’ behavior. It was shown that the first crack formed in the tensile corner of the door opening, and the subsequent cracks formed in the wall without a hole. Based on the changes in the value of the shear deformation angles, the phases of work of the stiffening walls were determined. The presented research results are only a part of an extensive study of stiffening walls in masonry buildings conducted at the Silesian University of Technology. Full article

(This article belongs to the Special Issue Masonry Structures and Reinforced Concrete Structures)

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17 pages, 6183 KiB

Open AccessArticle

Waste Glass Valorization as Raw Material in the Production of Portland Clinker and Cement

by Alina Bădănoiu, Adriana Moanță, Ovidiu Dumitrescu, Adrian Ionuț Nicoară and Roxana Trușcă

Materials 2022, 15(20), 7403; https://doi.org/10.3390/ma15207403 - 21 Oct 2022

Cited by 3 | Viewed by 1306

Abstract

The paper presents experimental results regarding the synthesis of Portland clinker starting from raw mixes based on two types of clayey precursors, i.e., clay and marl (the most common types of raw materials used in the cement industry), with and without glass waste [...] Read more.

The paper presents experimental results regarding the synthesis of Portland clinker starting from raw mixes based on two types of clayey precursors, i.e., clay and marl (the most common types of raw materials used in the cement industry), with and without glass waste content. The soda-lime glass waste addition (5.36–5.59 wt %), used to control the silica ratio of the raw mix, improved the raw mix burnability and decreased the calcination temperature (by 20 °C), leading to a decrease in fuel consumption and contributing to the reduction in CO₂ emissions associated with clinker and cement production. The clinkers obtained by the calcination of raw mixes with glass waste content at 1430 °C with a 30 min plateau had a similar mineralogical composition and microstructure to the clinkers obtained from the reference raw mixes and fulfilled the requirements of the specific standard EN 197-1. The obtained clinkers were used to produce two types of Portland cement, i.e., a unitary cement (CEM I) and a binary blended cement with slag (CEM II/B-S). The main characteristics of these cements, i.e., loss on ignition, insoluble residue, sulfate and chloride contents, as well as the setting time and soundness, meet the conditions stipulated in the EN 197-1 standard. The values of compressive strength, assessed on mortars after 2, 7 and 28 days of curing, allow the classification of all CEM I cements in the 42.5 R class. In the case of CEM II/B-S cements, those obtained from raw mixes with clay can be classified in the 42.5 N class, while those obtained from raw mixes with marl are classified in the 32.5 R class. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Multipurpose Applications of Advanced Micro and Nanomaterials Used in Life and Materials Science)

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13 pages, 10296 KiB

Open AccessArticle

Hot Deformation Behavior and Processing Maps of ZnSnO₃/Cu Composites

by Wei-Jian Li, Zi-Yao Chen, Xiao-Peng Tang, Wen-Zhu Shao and Liang Zhen

Materials 2022, 15(20), 7402; https://doi.org/10.3390/ma15207402 - 21 Oct 2022

Cited by 2 | Viewed by 993

Abstract

In this work, we designed ternary ZnSnO₃ particle-reinforced Cu matrix composites and evaluated the hot deformation behavior of ZnSnO₃/Cu composites. The hot deformation characteristics of typical dynamic recrystallization were probed by the resulting true stress–strain curves of ZnSnO₃/Cu [...] Read more.

In this work, we designed ternary ZnSnO₃ particle-reinforced Cu matrix composites and evaluated the hot deformation behavior of ZnSnO₃/Cu composites. The hot deformation characteristics of typical dynamic recrystallization were probed by the resulting true stress–strain curves of ZnSnO₃/Cu composites. The influences of deformation conditions, including temperatures (650–850 °C) and strain rates (0.01–5 s⁻¹), on the flow stress of the designed composites were investigated. This revealed that the peak stress increased with the increasing of strain rate and decreasing of temperature. Additionally, the activation energy was calculated to be 237.05 kJ/mol and followed by yielding a constitutive equation for low-stress ZnSnO₃/Cu composites. The processing maps established by dynamic materials model theory indicated that the designed composites possessed excellent hot workability, and then the processing parameters (790–850 °C and 0.01–0.04 s⁻¹) of the ZnSnO₃/Cu composites were determined for practical industrial production. Our work discloses the deformation behavior of ZnSnO₃/Cu matrix composites and extends the rational process design for ternary ceramic/metal materials with excellent hot workability. Full article

(This article belongs to the Special Issue Manufacturing and Mechanical Properties of Metal Matrix Composites)

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20 pages, 8405 KiB

Open AccessArticle

Thermo-Mechanical Coupling Model of Bond-Based Peridynamics for Quasi-Brittle Materials

by Haoran Zhang, Lisheng Liu, Xin Lai, Hai Mei and Xiang Liu

Materials 2022, 15(20), 7401; https://doi.org/10.3390/ma15207401 - 21 Oct 2022

Cited by 2 | Viewed by 1241

Abstract

The mechanical properties of quasi-brittle materials, which are widely used in engineering applications, are often affected by the thermal condition of their service environment. Moreover, the materials appear brittle when subjected to tensile loading and show plastic characteristics under high pressure. These two [...] Read more.

The mechanical properties of quasi-brittle materials, which are widely used in engineering applications, are often affected by the thermal condition of their service environment. Moreover, the materials appear brittle when subjected to tensile loading and show plastic characteristics under high pressure. These two phenomena manifest under different circumstances as completely different mechanical behaviors in the material. To accurately describe the mechanical response, the material behavior, and the failure mechanism of quasi-brittle materials with the thermo-mechanical coupling effect, the influence of the thermal condition is considered in calculating bond forces in the stretching and compression stages, based on a new bond-based Peridynamic (BB-PD) model. In this study, a novel bond-based Peridynamic, fully coupled, thermo-mechanical model is proposed for quasi-brittle materials, with a heat conduction component to account for the effect of the thermo-mechanical coupling. Numerical simulations are carried out to demonstrate the validity and capability of the proposed model. The results reveal that agreement could be found between our model and the experimental data, which show good reliability and promise in the proposed approach. Full article

(This article belongs to the Special Issue Modeling and Analysis of Damage and Failure of Concrete-Like, Brittle and Quasi-brittle Materials)

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8 pages, 1414 KiB

Open AccessArticle

Ionic Liquid Mixture Electrolyte Matching Porous Carbon Electrodes for Supercapacitors

by Yuhua Zhao, Yujuan Chen, Quanzhou Du, Kelei Zhuo, Lifang Yang, Dong Sun and Guangyue Bai

Materials 2022, 15(20), 7400; https://doi.org/10.3390/ma15207400 - 21 Oct 2022

Cited by 2 | Viewed by 1219

Abstract

Ionic liquids (ILs), with their wide electrochemical stable potential window, are promising electrolytes for supercapacitors (SCs). The suitable matching of the ion size and shape of the ILs to the pore size and structure of porous carbon (PC) electrode materials can realize the [...] Read more.

Ionic liquids (ILs), with their wide electrochemical stable potential window, are promising electrolytes for supercapacitors (SCs). The suitable matching of the ion size and shape of the ILs to the pore size and structure of porous carbon (PC) electrode materials can realize the enhanced capacitive performance of the SCs. Here we report an interesting result: The capacitance of PC-based SCs shows a quasi-sinusoidal relationship with the composition (mass fraction) of the binary IL mixture as the electrolyte. This relationship is also interpreted based on the matching between the pore sizes of the PC materials and the size/shape of various ions of the IL mixture electrolyte. This can provide a new strategy to improve the performance of SCs by formulating a suitable mixture of different ILs to match the carbon-based electrode materials with a special pore size distribution. Full article

(This article belongs to the Special Issue Nano and Advanced Material Engineering)

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20 pages, 3417 KiB

Open AccessArticle

Fused Filament Fabrication of Alumina/Polymer Filaments for Obtaining Ceramic Parts after Debinding and Sintering Processes

by Claudio Tosto, Mario Bragaglia, Francesca Nanni, Giuseppe Recca and Gianluca Cicala

Materials 2022, 15(20), 7399; https://doi.org/10.3390/ma15207399 - 21 Oct 2022

Cited by 7 | Viewed by 2228

Abstract

In this paper, a hybrid commercially available alumina/polymer filament was 3D printed and thermally treated (debinding and sintering) to obtain ceramic parts. Microscopic and spectroscopic analysis was used to thoroughly characterize the green and sintered parts in terms of their mesostructured, as well [...] Read more.

In this paper, a hybrid commercially available alumina/polymer filament was 3D printed and thermally treated (debinding and sintering) to obtain ceramic parts. Microscopic and spectroscopic analysis was used to thoroughly characterize the green and sintered parts in terms of their mesostructured, as well as their flexural properties. The sintered samples show an α alumina crystalline phase with a mean density of 3.80 g/cm³, a tensile strength of 232.6 ± 12.3 MPa, and a Vickers hardness of 21 ± 0.7 GPa. The mean thermal conductivity value at room temperature was equal to 21.52 ± 0.02 W/(mK). The values obtained through FFF production are lower than those obtained by conventional processes as the 3D-printed samples exhibited imperfect interlayer bonding and voids similar to those found in the structures of polymeric FFFs. Nonetheless, the highly filled ceramic filament is suitable for use in affordable and easy-to-operate FFF machines, as shown by the cost analysis of a real printed and sintered FFF part. Full article

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14 pages, 4225 KiB

Open AccessArticle

Reducing Surface Roughness of 3D Printed Short-Carbon Fiber Reinforced Composites

by Raluca Maier, Sebastian-Gabriel Bucaciuc and Andrei Cristian Mandoc

Materials 2022, 15(20), 7398; https://doi.org/10.3390/ma15207398 - 21 Oct 2022

Cited by 4 | Viewed by 1460

Abstract

A 100 W fibre laser source was used to minimize the surface roughness of 3D-printed Onyx parts. Furthermore, this study aimed to determine the mechanism of surface finishing, the influence of the laser process parameters (laser power, pulse frequency, and laser scanning path) [...] Read more.

A 100 W fibre laser source was used to minimize the surface roughness of 3D-printed Onyx parts. Furthermore, this study aimed to determine the mechanism of surface finishing, the influence of the laser process parameters (laser power, pulse frequency, and laser scanning path) on the surface morphology, and the influence of the scanning path on the dimensional accuracy of the investigated Onyx 3D-printed specimens. A significant reduction in surface roughness of 91.15% was achieved on the S3 Onyx 3D-printed specimen following laser surface polishing treatment using a 50 W laser power and a frequency of 50 kHz. The laser scanning path had little influence on the surface roughness, but had a major impact on the geometrical deviation of the treated sample. Full article

(This article belongs to the Special Issue 3D Printing: Materials, Properties, and Applications)

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18 pages, 8384 KiB

Open AccessArticle

Quick Curing Mechanisms for All-Season Paints and Renders

by Ivan Cabrera, Markus Rückel, Volodymyr Boyko, Roland Baumstark and Immanuel Willerich

Materials 2022, 15(20), 7397; https://doi.org/10.3390/ma15207397 - 21 Oct 2022

Cited by 1 | Viewed by 1624

Abstract

Paints and coatings are required to quickly cure under a broad variety of environmental conditions and deliver solid long-term performance. Achieving a balance during all seasons between quick curing of a coating film, i.e., early rain resistance, while maintaining sufficient workability and open [...] Read more.

Paints and coatings are required to quickly cure under a broad variety of environmental conditions and deliver solid long-term performance. Achieving a balance during all seasons between quick curing of a coating film, i.e., early rain resistance, while maintaining sufficient workability and open time for an optimized aesthetic appearance is a challenge for the architectural coatings industry. This article describes how the colloidal physics differs between the current standard mechanism to achieve early rain resistance by inhibited coagulants in winter paints and a new mechanism that provides all-season paints. A combination of advanced physical characterization methods, such as electrophoretic mobility, dynamic light scattering and confocal laser scanning microscopy, in combination with application tests, is used to provide a comprehensive mechanism of the early rain resistance achieved by such paints. In addition, it is shown that this new system can be transferred to wood coatings and organic renders. The key finding of this article is that all-season paints combining early rain resistance at cold and damp conditions with open time at high temperatures and dry conditions rely on fast paint film formation with high early integrity rather than coagulants triggered by base evaporation. Full article

(This article belongs to the Special Issue Recent Advances in Coatings, Adhesives and Construction Materials)

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13 pages, 3536 KiB

Open AccessArticle

Investigating the Effect of PCL Concentrations on the Characterization of PLA Polymeric Blends for Biomaterial Applications

by Solechan Solechan, Agus Suprihanto, Susilo Adi Widyanto, Joko Triyono, Deni Fajar Fitriyana, Januar Parlaungan Siregar and Tezara Cionita

Materials 2022, 15(20), 7396; https://doi.org/10.3390/ma15207396 - 21 Oct 2022

Cited by 3 | Viewed by 1915

Abstract

Polylactic acid (PLA) and polycaprolactone (PCL) are synthetic polymers that are extensively used in biomedical applications. However, the PLA/PCL blend produced by ball milling, followed by pressure compaction and sintering, has not been extensively explored. The goal of this research is to investigate [...] Read more.

Polylactic acid (PLA) and polycaprolactone (PCL) are synthetic polymers that are extensively used in biomedical applications. However, the PLA/PCL blend produced by ball milling, followed by pressure compaction and sintering, has not been extensively explored. The goal of this research is to investigate the effect of the composition of biomaterials derived from PLA and PCL prepared by ball milling, followed by pressure compaction and sintering, on mechanical and physical properties. PCL and PLA with various concentrations were blended utilizing a ball milling machine for 2 h at an 80-rpm rotation speed. The obtained mixture was placed in a stainless steel 304 mold for the compacting process, which uses a pressure of 30 MPa to create a green body. The sintering procedure was carried out on the green body created at 150 °C for 2 h using a digital oven. The obtained PLA/PCL blend was tested using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), density, porosity, and three-point bending. Following the interaction between PCL and PLA in the PLA/PCL blend, the FTIR spectra and XRD diffractograms obtained in this work revealed a number of modifications in the functional groups and crystal phase. The 90PLA specimen had the best mechanical properties, with a maximum force and displacement of 51.13 N and 7.21 mm, respectively. The porosity of the PLA/PCL blend decreased with increasing PLA concentration so that the density and flexural properties of the PLA/PCL blend increased. The higher PCL content decreased the stiffness of the PLA molecular chain, consequently reducing its flexural properties. Full article

(This article belongs to the Special Issue Synthesis, Performance and Application of Polymers Materials)

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22 pages, 3366 KiB

Open AccessArticle

Prediction of Corrosion-Induced Longitudinal Cracking Time of Concrete Cover Surface of Reinforced Concrete Structures under Load

by Jian Wang, Yongyu Yuan, Qiang Xu and Hongtu Qin

Materials 2022, 15(20), 7395; https://doi.org/10.3390/ma15207395 - 21 Oct 2022

Cited by 3 | Viewed by 1125

Abstract

Reinforced concrete (RC) structures suffer from different types of loads during service life, and the corrosion characteristics of steel bars embedded in concrete under load are different from those under non-load. In this paper, when the interface between steel bars and concrete (IBSC) [...] Read more.

Reinforced concrete (RC) structures suffer from different types of loads during service life, and the corrosion characteristics of steel bars embedded in concrete under load are different from those under non-load. In this paper, when the interface between steel bars and concrete (IBSC) cracked and the concrete cover surface (CCS) cracked, the effects of load on the critical corrosion depth of steel bars were analysed based on the thick-walled cylinder model, and a prediction model for the corrosion-induced longitudinal cracking (CLC) time (i.e., initiation cracking time) of the CCS of RC structures under load was proposed. Finally, the influence of load on the CLC time of CCS was discussed on the basis of the proposed prediction model. The results showed that the load had a significant effect on the critical corrosion depth of steel bars when the IBSC cracked induced by corrosion, while the influence of load on the critical corrosion depth of steel bars when the CCS cracked induced by corrosion was not obvious. When the CCS cracks induced by corrosion under load, the influence of the rust-filling layer on the critical corrosion depth of steel bars was larger than that of the load. With the increase in load, the CLC time of CCS decreased. The calculated values of the proposed prediction model were in reasonable agreement with the experimental values, which can provide a reference for durability evaluation and service life prediction of RC structures and lay the foundation for the investigation of the corrosion depth of steel bars in concrete under load. Full article

(This article belongs to the Special Issue Corrosion of Reinforced Concrete Structures in Civil Engineering and Architecture)

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25 pages, 75269 KiB

Open AccessArticle

Experimental Study on the Influence of Different Factors on the Mechanical Properties of a Soil–Rock Mixture Solidified by Micro-Organisms

by Yongshuai Sun, Jianguo Lv, Ya Tuo and Guihe Wang

Materials 2022, 15(20), 7394; https://doi.org/10.3390/ma15207394 - 21 Oct 2022

Cited by 1 | Viewed by 1387

Abstract

In this paper, we focus on the application of mechanical properties in a soil–rock mixture modified by microbial mineralization under the influence of different factors, including pH value, cementing solution concentration, and cementing time. Cementing fluids and samples with different pH values, calcium [...] Read more.

In this paper, we focus on the application of mechanical properties in a soil–rock mixture modified by microbial mineralization under the influence of different factors, including pH value, cementing solution concentration, and cementing time. Cementing fluids and samples with different pH values, calcium ion concentrations, and mineralization cementation were prepared. The process of urea hydrolysis MICP under different factors was studied. A solidified soil–rock mixture sample under triaxial compression was measured. Then, combined with scanning test methods, such as SEM and XRD, the influence of different factors on the mechanical strength and failure mode of the soil–rock mixture structure was analyzed from a microscopic point of view. The results show that a low concentration of cementing solution with a high concentration of bacteria liquid generated the highest calcium carbonate content and the strongest cementing ability. When the pH value of the cementation solution is six, the cementation effect between the pores is the best, and the deviatoric stress is stronger. When wet-curing samples, short or long curing time will adversely affect the strength of soil–rock mixture samples, the strongest curing and cementing ability is 5 days. The microscopic results show that the microbial mineralization technology fills the pores between the particles, and the interaction force between particles is enhanced to enhance the strength of the soil–rock mixture. Full article

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14 pages, 3976 KiB

Open AccessArticle

Mathematical Models and Experiments on the Acoustic Properties of Granular Packing Structures (Measurement of Tortuosity in Hexagonal Close-Packed and Face-Centered Cubic Lattices)

by Shuichi Sakamoto, Kyosuke Suzuki, Kentaro Toda and Shotaro Seino

Materials 2022, 15(20), 7393; https://doi.org/10.3390/ma15207393 - 21 Oct 2022

Cited by 2 | Viewed by 1172

Abstract

In this study, the sound absorption characteristics of hexagonal close-packed and face-centered cubic lattices were estimated by theoretical analysis. Propagation constants and characteristic impedances were obtained by dividing each structure into elements perpendicular to the incident direction of sound waves and by approximating [...] Read more.

In this study, the sound absorption characteristics of hexagonal close-packed and face-centered cubic lattices were estimated by theoretical analysis. Propagation constants and characteristic impedances were obtained by dividing each structure into elements perpendicular to the incident direction of sound waves and by approximating each element to a clearance between two parallel planes. Consequently, the propagation constant and the characteristic impedance were treated as a one-dimensional transfer matrix in the propagation of sound waves, and the normal incident sound absorption coefficient was calculated by the transfer matrix method. The theoretical value of the sound absorption coefficient was derived by using the effective density applied to the measured tortuosity. As a result, the theoretical value was becoming closer to the measured value. Therefore, the measured tortuosity is reasonable. Full article

(This article belongs to the Special Issue Advanced Materials Structures for Sound and Vibration Damping)

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17 pages, 5175 KiB

Open AccessArticle

Experimental Investigations and Effect of Nano-Powder-Mixed EDM Variables on Performance Measures of Nitinol SMA

by Rakesh Chaudhari, Yug Shah, Sakshum Khanna, Vivek K. Patel, Jay Vora, Danil Yurievich Pimenov and Khaled Giasin

Materials 2022, 15(20), 7392; https://doi.org/10.3390/ma15207392 - 21 Oct 2022

Cited by 9 | Viewed by 1402

Abstract

In the present study, the effect of alumina (Al₂O₃) nano-powder was investigated for the electrical discharge machining (EDM) of a Nitinol shape memory alloy (SMA). In addition to the nano-powder concentration, other parameters of pulse-on-time (T_on), pulse-off-time [...] Read more.

In the present study, the effect of alumina (Al₂O₃) nano-powder was investigated for the electrical discharge machining (EDM) of a Nitinol shape memory alloy (SMA). In addition to the nano-powder concentration, other parameters of pulse-on-time (T_on), pulse-off-time (T_off), and current were selected for the performance measures of the material removal rate (MRR), surface roughness (SR), and tool wear rate (TWR) of Nitinol SMA. The significance of the design variables on all the output measures was analyzed through an analysis of variance (ANOVA). The regression model term has significantly impacted the developed model terms for all the selected measures. In the case of individual variables, Al₂O₃ powder concentration (PC), T_off, and T_on had significantly impacted MRR, TWR, and SR measures, respectively. The influence of EDM variables were studied through main effect plots. The teaching–learning-based optimization (TLBO) technique was implemented to find an optimal parametric setting for attaining the desired levels of all the performance measures. Pursuant to this, the optimal parametric settings of current at 24 A, PC at 4 g/L, T_off at 10 µs, and T_on of 4 µs have shown optimal input parameters of 43.57 mg/min for MRR, 6.478 mg/min for TWR, and 3.73 µm for SR. These results from the TLBO technique were validated by performing the experiments at the optimal parametric settings of the EDM process. By considering the different user and application requirements, 40 Pareto points with unique solutions were generated. Lastly, scanning electron microscopy (SEM) performed the machined surface analysis. The authors consider this to be very beneficial in the nano-powder-mixed EDM process for appropriate manufacturing operations. Full article

(This article belongs to the Special Issue Ultra-Precision Manufacturing Technology for Difficult-to-Machine Materials)

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15 pages, 3497 KiB

Open AccessReview

3D Printing Technology for Smart Clothing: A Topic Review

by Shuangqing Wu, Taotao Zeng, Zhenhua Liu, Guozhi Ma, Zhengyu Xiong, Lin Zuo and Zeyan Zhou

Materials 2022, 15(20), 7391; https://doi.org/10.3390/ma15207391 - 21 Oct 2022

Cited by 7 | Viewed by 4709

Abstract

Clothing is considered to be an important element of human social activities. With the increasing maturity of 3D printing technology, functional 3D printing technology can realize the perfect combination of clothing and electronic devices while helping smart clothing to achieve specific functions. Furthermore, [...] Read more.

Clothing is considered to be an important element of human social activities. With the increasing maturity of 3D printing technology, functional 3D printing technology can realize the perfect combination of clothing and electronic devices while helping smart clothing to achieve specific functions. Furthermore, the application of functional 3D printing technology in clothing not only provides people with the most comfortable and convenient wearing experience, but also completely subverts consumers’ perception of traditional clothing. This paper introduced the progress of the application of 3D printing from the aspect of traditional clothing and smart clothing through two mature 3D printing technologies normally used in the field of clothing, and summarized the challenges and prospects of 3D printing technology in the field of smart clothing. Finally, according to the analysis of the gap between 3D-printed clothing and traditionally made clothing due to the material limitations, this paper predicted that the rise in intelligent materials will provide a new prospect for the development of 3D-printed clothing. This paper will provide some references for the application research of 3D printing in the field of smart clothing. Full article

(This article belongs to the Special Issue Photoelectric Functional Materials and Devices)

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19 pages, 7560 KiB

Open AccessArticle

Intermediate Crack Debonding of Externally Bonded FRP Reinforcement—Comparison of Methods

by Paweł Tworzewski, Jeffrey K. Alexy and Robert W. Barnes

Materials 2022, 15(20), 7390; https://doi.org/10.3390/ma15207390 - 21 Oct 2022

Cited by 2 | Viewed by 1198

Abstract

Many researchers around the world have made extensive efforts to study the phenomenon of fiber-reinforced polymer (FRP) debonding. Based on these efforts, code provisions and various models have been proposed for predicting intermediate crack (IC) debonding failure. The paper presents a comparison of [...] Read more.

Many researchers around the world have made extensive efforts to study the phenomenon of fiber-reinforced polymer (FRP) debonding. Based on these efforts, code provisions and various models have been proposed for predicting intermediate crack (IC) debonding failure. The paper presents a comparison of seven selected models: fib bulletin 14 approach, Teng et al. model, Lu model, Seracino et al. model, Said and Wu model, Elsanadedy et al. model and ACI 440. The accuracy of each model was evaluated based on the test results of 58 flexural specimens with IC debonding failures of externally bonded (EB), carbon FRP plates or sheets found in the existing literature. The experimental database was prepared to include a wide range of parameters affecting the issue under consideration. A comparison of the measured and predicted load capacity values was made to evaluate the prediction accuracy of the considered models. The analysis included the limitation of the load capacity estimated based on IC debonding models as well as concrete crushing and FRP rupture types of failure. The results indicate that the latest models proposed for direct implementation in design guidelines—the Said and Wu model and the Elsanadedy et al. model—offer the best accuracy in predicting the load capacity. In contrast, the fib bulletin 14 approach shows a wide dispersion of predictions and a large proportion of highly overestimated results. Full article

(This article belongs to the Special Issue Advanced Composite Materials: Theory, Design and Applications)

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17 pages, 6110 KiB

Open AccessArticle

Calorimetric Method for the Testing of Thermal Coefficients of the TIG Process

by Marek Mróz, Antoni Władysław Orłowicz, Magdalena Lenik, Andrzej Trytek and Mirosław Tupaj

Materials 2022, 15(20), 7389; https://doi.org/10.3390/ma15207389 - 21 Oct 2022

Viewed by 986

Abstract

This paper presents an original design of a test apparatus for calorimetric measurements of arc efficiency η and melting efficiency η_m in welding processes. The construction and principle of operation of a new flow calorimeter are described, as well as the method [...] Read more.

This paper presents an original design of a test apparatus for calorimetric measurements of arc efficiency η and melting efficiency η_m in welding processes. The construction and principle of operation of a new flow calorimeter are described, as well as the method for determining the η and η_m values in the process of the surface melting of aluminium–silicon alloy casting surfaces with a concentrated heat flux generated by the TIG (Tungsten Inert Gas) method. The results obtained indicate the advisability of using calorimetric testing to assess the arc efficiency of welding processes. It was demonstrated that changing the welding current and arc scanning speed, as well as changing the chemical composition of the silumin, has an effect on the arc efficiency value η. This has the effect of introducing a different amount of heat into the area of the heated material. The consequence of this is a change in the value of the melting efficiency η_m, which results in a change in the width and depth of the surface melting areas, through this, the cooling conditions of the material. As is well known, this will affect the microstructure of the welds and the width and microstructure of the heat-affected zone, and thus the performance of the welded joints. Full article

(This article belongs to the Special Issue Advanced Technologies of Welding, Surfacing, and Thermal Spraying of Modern Materials)

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27 pages, 6863 KiB

Open AccessArticle

An Analytical and Experimental Study on Cutting Characteristics and Transient Cutting Force Modeling in Feed Directional Ultrasonic Vibration-Assisted Cutting of High Strength Alloys

by Xuelin Chen, Jinyuan Tang, Wen Shao, Bo Hu and Jinxiang Ye

Materials 2022, 15(20), 7388; https://doi.org/10.3390/ma15207388 - 21 Oct 2022

Cited by 2 | Viewed by 1454

Abstract

Ultrasonic vibration-assisted cutting (UVC) is progressively being used in machining as it can significantly promote the fabrication process. However, the ultrasonic vibration affecting the cutting process is still controversial. The full-transient cutting process is proposed in this study to analyze the affecting mechanism [...] Read more.

Ultrasonic vibration-assisted cutting (UVC) is progressively being used in machining as it can significantly promote the fabrication process. However, the ultrasonic vibration affecting the cutting process is still controversial. The full-transient cutting process is proposed in this study to analyze the affecting mechanism induced by ultrasonic vibration in the cutting process. This novel model is the first developed based on the fact that ultrasonic vibration would change mechanical behaviors and the cutting process. For example, the reduction of shear flowing stress in the primary shear zone and alteration of the shear angle in the UVC process. Then, considering those coupled effects, a novel model is proposed to determine the average and transient cutting forces. Here, insight and understanding into the physical phenomenon in UVC are provided. The effectiveness of the proposed model is verified by comparison with experimental results and analytical models available in the literature, with cutting parameters varying from macro to micro-scale. The results show that the ultrasonic vibration affects the cutting process in a complicated way, which is determined by transient characteristics, acoustic softening, thermal softening, plowing, and friction. Those effects on cutting performances in the UVC process under various cutting scenarios are investigated and discussed systematically. The average deviation of cutting forces between experiments and values predicted by the proposed model for Ti6Al4V, AISI 1045, and Al6063 is about 7%, 10.2%, and 11%, respectively. The deviation decreases with the increase of cutting speed in the machining of Ti6Al4V, which is different from the machining of other materials. This is contributed by the varied effect of ultrasonic vibration on the cutting process. Full article

(This article belongs to the Special Issue The Advanced Manufacturing Technologies of Metal Gears)

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15 pages, 5693 KiB

Open AccessArticle

Numerical Study of the Mechanical Behaviour of Wedge-Shaped Defect Filling Materials

by Lyaysan Sakhabutdinova, Anna A. Kamenskikh, Alex G. Kuchumov, Yuriy Nosov and Inessa Baradina

Materials 2022, 15(20), 7387; https://doi.org/10.3390/ma15207387 - 21 Oct 2022

Cited by 2 | Viewed by 1446

Abstract

This paper deals with direct restorations of teeth with non-carious cervical lesions (NCCL). NCCL defects are capable of gradual growth and are accompanied by the degradation of the surrounding tissue. Direct restorative treatment, in which the cavity is filled with a cementing agent, [...] Read more.

This paper deals with direct restorations of teeth with non-carious cervical lesions (NCCL). NCCL defects are capable of gradual growth and are accompanied by the degradation of the surrounding tissue. Direct restorative treatment, in which the cavity is filled with a cementing agent, is considered to be an accessible and common treatment option. The study included simulations of the teeth without lesions, the teeth with V and U lesions and the tooth-restorative system. Parameterised numerical tooth models were constructed. Two cases with defect depths of 0.8 mm and ~1.7 mm and three variants with fillet radii of the defect end of 0.1, 0.2 and 0.3 mm were considered. The effect of two biomaterials for restorations was studied, namely Herculite XRV (Kerr Corp, Orange, CA, USA) and Charisma (Heraeus Kulzer GmbH, Hanau, Germany). The models were deformed with a vertical load of 100 to 1000 N from the antagonist tooth. The tooth-restorative system was considered, taking into consideration the contact interaction in the interface areas with the tooth tissues. Within the limits of the research, the character of the distribution of the deformation characteristics and their dependence on the level of loading, the depth of the defect and the radius of the curvature of the “wedge” were established. Full article

(This article belongs to the Special Issue Applications of Dental Biomaterials)

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32 pages, 15559 KiB

Open AccessArticle

High-Temperature Mechanical Properties of Stress-Relieved AlSi10Mg Produced via Laser Powder Bed Fusion Additive Manufacturing

by Dirk Lehmhus, Thomas Rahn, Adrian Struss, Phillip Gromzig, Tim Wischeropp and Holger Becker

Materials 2022, 15(20), 7386; https://doi.org/10.3390/ma15207386 - 21 Oct 2022

Cited by 8 | Viewed by 2043

Abstract

The present study is dedicated to the evaluation of the mechanical properties of an additively manufactured (AM) aluminum alloy and their dependence on temperature and build orientation. Tensile test samples were produced from a standard AlSi10Mg alloy by means of the Laser Powder [...] Read more.

The present study is dedicated to the evaluation of the mechanical properties of an additively manufactured (AM) aluminum alloy and their dependence on temperature and build orientation. Tensile test samples were produced from a standard AlSi10Mg alloy by means of the Laser Powder Bed Fusion (LPBF) or Laser Beam Melting (LBM) process at polar angles of 0°, 45° and 90°. Prior to testing, samples were stress-relieved on the build platform for 2 h at 350 °C. Tensile tests were performed at four temperature levels (room temperature (RT), 125, 250 and 450 °C). Results are compared to previously published data on AM materials with and without comparable heat treatment. To foster a deeper understanding of the obtained results, fracture surfaces were analyzed, and metallographic sections were prepared for microstructural evaluation and for additional hardness measurements. The study confirms the expected significant reduction of strength at elevated temperatures and specifically above 250 °C: Ultimate tensile strength (UTS) was found to be 280.2 MPa at RT, 162.8 MPa at 250 °C and 34.4 MPa at 450 °C for a polar angle of 0°. In parallel, elongation at failure increased from 6.4% via 15.6% to 26.5%. The influence of building orientation is clearly dominated by the temperature effect, with UTS values at RT for polar angles of 0° (vertical), 45° and 90° (horizontal) reaching 280.2, 272.0 and 265.9 MPa, respectively, which corresponds to a 5.1% deviation. The comparatively low room temperature strength of roughly 280 MPa is associated with stress relieving and agrees well with data from the literature. However, the complete breakdown of the cellular microstructure reported in other studies for treatments at similar or slightly lower temperatures is not fully confirmed by the metallographic investigations. The data provide a basis for the prediction of AM component response under the thermal and mechanical loads associated with high-pressure die casting (HPDC) and thus facilitate optimizing HPDC-based compound casting processes involving AM inserts. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches (Volume II))

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12 pages, 2369 KiB

Open AccessArticle

Using Physical Modeling to Optimize the Aluminium Refining Process

by Tomáš Prášil, Ladislav Socha, Karel Gryc, Jana Svizelová, Mariola Saternus, Tomasz Merder, Jacek Pieprzyca and Martin Gráf

Materials 2022, 15(20), 7385; https://doi.org/10.3390/ma15207385 - 21 Oct 2022

Cited by 4 | Viewed by 1150

Abstract

Concern for the environment and rational management of resources requires the development of recoverable methods of obtaining metallic materials. This also applies to the production of aluminium and its alloys. The quality requirements of the market drive aluminium producers to use effective refining [...] Read more.

Concern for the environment and rational management of resources requires the development of recoverable methods of obtaining metallic materials. This also applies to the production of aluminium and its alloys. The quality requirements of the market drive aluminium producers to use effective refining methods, and one of the most commonly used is blowing an inert gas into liquid aluminium via a rotating impeller. The efficiency and cost of this treatment depends largely on the application of the correct ratios between the basic parameters of the process, which are the flow rate of the inert gas, the speed of the rotor and the duration of the process. Determining these ratios in production conditions is expensive and difficult. This article presents the results of research aimed at determining the optimal ratio of the inert gas flow rate to the rotary impeller speed, using physical modeling techniques for the rotor as used in industrial conditions. The tests were carried out for rotary impeller speeds from 150 to 550 rpm and gas flow rates of 12, 17 and 22 dm³/min. The research was carried out on a 1:1 scale physical model, and the results, in the form of visualization of the degree of gas-bubble dispersion, were assessed on the basis of the five typical dispersion patterns. The removal of oxygen from water was carried out analogously to the process of removing hydrogen from aluminium. The curves of the rate of oxygen removal from the model liquid were determined, showing the course of oxygen reduction during refining with the same inert gas flows and rotor speeds mentioned above. Full article

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17 pages, 3760 KiB

Open AccessArticle

Preparation and Application of Foaming Agent Based on the Compound System of Short-Chain Fluorocarbon and Soybean Residue Protein

by Ning Song, Zhihe Li, Shaoqing Wang and Yuanliang Xiong

Materials 2022, 15(20), 7384; https://doi.org/10.3390/ma15207384 - 21 Oct 2022

Cited by 4 | Viewed by 1320

Abstract

This study provides a new idea for the design of an advanced foaming agent with soybean residue protein (SRP) as a potential protein source. In order to achieve the most effective foaming performance, we employed the novel approach of response surface methodology (RSM) [...] Read more.

This study provides a new idea for the design of an advanced foaming agent with soybean residue protein (SRP) as a potential protein source. In order to achieve the most effective foaming performance, we employed the novel approach of response surface methodology (RSM) to improve important process parameters in a hot-alkali experiment. The experimental results showed that the optimum reaction parameters of pH and temperature were pH 10.2 and 50.5 °C, respectively, which, when continued for 3 h, led to the highest foaming property of the SRP foaming agent (486 mL). Based on the scheme, we also designed an experiment whereby we incorporated 1.0g/L FS-50 into the SRP foaming agent (SRP-50) to achieve higher foaming capacity compared with the commercial foaming agent. This foaming agent was cheaper than commercial vegetable protein foaming agents (12 USD/L) at 0.258 USD/L. Meanwhile, the properties of foam concrete prepared using SRP-50 were studied in comparison with a commercial vegetable protein foaming agent (PS). The results demonstrated that the foam prepared using SRP-50 had better stability, and the displacement of the foam decreased by 10% after 10 min. During the curing period, the foam concrete possesseda compressive strength of 5.72 MPa after 28 days, which was an increase from 2.95 MPa before. The aperture of the foam ranged from 100 to 500 μm with the percentage increasing up to 71.5%, which indicated narrower pore-size distribution and finer pore size. In addition, the shrinkage of the foam concrete was also improved. These findings not only achieve the utilization of waste but also provide a new source for protein foaming agents. Full article

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19 pages, 5356 KiB

Open AccessArticle

Development and Application of Carbonate Dissolution Test Equipment under Thermal–Hydraulic–Chemical Coupling Condition

by Jinzhu Meng, Sili Chen, Junxiang Wang, Zhi Chen and Jingyu Zhang

Materials 2022, 15(20), 7383; https://doi.org/10.3390/ma15207383 - 21 Oct 2022

Cited by 4 | Viewed by 1455

Abstract

The latest continuous flow micro reaction technology was adopted to independently develop carbonate rock dissolution test equipment. Carbonate rock dissolution tests were conducted under different temperatures, flow rates, and dynamic water pressure conditions to study the dissolution process of carbonate rocks under the [...] Read more.

The latest continuous flow micro reaction technology was adopted to independently develop carbonate rock dissolution test equipment. Carbonate rock dissolution tests were conducted under different temperatures, flow rates, and dynamic water pressure conditions to study the dissolution process of carbonate rocks under the coupling of heat-water-chemistry. The dissolution effect and development law of carbonate rocks were explored by quantitatively studying carbonate rock dissolution rate and chemical composition of karst water. The results showed that the self-designed dissolution test equipment has obvious advantages. After dissolution, carbonate rock specimens were damaged to varying degrees. The dissolution rate was proportional to water velocity and hydrodynamic pressure, with the velocity effect being greater than the hydrodynamic pressure effect. The pH value, conductivity, and Ca²⁺ ion content of the reaction solution gradually increased after dissolution. The development and application of the equipment have proved that, at low dynamic water pressures (2 MPa), the water flow velocity effect on the dissolution velocity was 1.5 times that when the dynamic water pressure was high (6 MPa); at a low water flow velocity of 15 mL/min, the dynamic water pressure effect on the dissolution velocity was three times that when the water flow velocity was high (75 mL/min). The development process is gradually becoming strong and stable. Its research has important theoretical significance and engineering application value to provide technical means and guarantee for the early identification, karst development, and safety evaluation of karst geological disasters. Full article

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11 pages, 1312 KiB

Open AccessArticle

Birch Tar Introduced into Polylactide and Its Influence on the Barrier, Thermal, Functional and Biological Properties of the Film Obtained by Industrial Extrusion

by Agnieszka Richert, Rafał Malinowski, Magda Ringwelska and Grażyna B. Dąbrowska

Materials 2022, 15(20), 7382; https://doi.org/10.3390/ma15207382 - 21 Oct 2022

Cited by 4 | Viewed by 1087

Abstract

The aim of the study was to evaluate possibility of producing a polylactide film with birch tar by the industrial extrusion method and whether the addition of 10% birch tar can ensure adequate biocidal properties of PLA against pathogenic microorganisms (E. coli [...] Read more.

The aim of the study was to evaluate possibility of producing a polylactide film with birch tar by the industrial extrusion method and whether the addition of 10% birch tar can ensure adequate biocidal properties of PLA against pathogenic microorganisms (E. coli, S. aureus, P. aeruginosa, A. tumefaciens, X. campestris, P. brassicacearum, P. corrugate and P. syringae) and fungi (A. niger, A. flavus and A. versicolor) while ensuring beneficial functional properties, such as water vapor, nitrogen, oxygen and carbon dioxide permeability, which are of considerable importance in the packaging industry. The main test methods used were ISO 22196, ISO 846, ISO 2556, ASTM F 1927 and ASTM F 2476-20. The obtained results prove the possibility of extruding polymer films with a biocidal additive, i.e., birch tar, and obtaining favorable properties that qualify the produced film for applications in the packaging industry. Full article

(This article belongs to the Special Issue Structure Property Relationship of Polymeric Materials)

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8 pages, 2708 KiB

Open AccessArticle

Crystal Structures and Electronic Properties of BaAu Compound under High Pressure

by Bingtan Li, Jianyun Wang, Shuai Sun and Hanyu Liu

Materials 2022, 15(20), 7381; https://doi.org/10.3390/ma15207381 - 21 Oct 2022

Viewed by 1010

Abstract

The investigations of Au-bearing alloy materials have been of broad research interest as their relevant features exhibit significant advantages compared with pure Au. Here, we extensively investigate the compression behaviors of BaAu compounds via first-principles calculations and find that a high-pressure cubic phase [...] Read more.

The investigations of Au-bearing alloy materials have been of broad research interest as their relevant features exhibit significant advantages compared with pure Au. Here, we extensively investigate the compression behaviors of BaAu compounds via first-principles calculations and find that a high-pressure cubic phase is calculated to be stable above 12 GPa. Further electronic calculations indicate that despite the low electronegativity of Ba, Fd-3m-structured BaAu exhibits metallic characteristics, which is different from those of semiconducting alkali metal aurides that possess slight characteristics of an ionic compound. These findings provide a step toward a further understanding of the electronic properties of BaAu compounds and provide key insight for exploring the other Au-bearing alloy materials under extreme conditions. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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16 pages, 11197 KiB

Open AccessArticle

The Tribological Properties of 30CrMnSiA Bearing Steels Treated by the Strengthening Grinding Process under Lubrication Wear

by Xiaochu Liu, Xiujie Chen, Zhongwei Liang, Tao Zou, Zhaoyang Liu, Jinrui Xiao, Dongwei Li and Diaodiao Yu

Materials 2022, 15(20), 7380; https://doi.org/10.3390/ma15207380 - 21 Oct 2022

Cited by 6 | Viewed by 1131

Abstract

This study used the strengthening grinding process (SGP) to treat the surface of 30CrMnSiA bearing steels. The effect of the jet angle of SGP on the tribological properties of 30CrMnSiA bearing steels under lubrication was investigated. The principle of enhancing wear resistance of [...] Read more.

This study used the strengthening grinding process (SGP) to treat the surface of 30CrMnSiA bearing steels. The effect of the jet angle of SGP on the tribological properties of 30CrMnSiA bearing steels under lubrication was investigated. The principle of enhancing wear resistance of 30CrMnSiA bearing steel ascribed to SGP was discussed in detail. The results showed that the lubrication properties and surface hardness of the 30CrMnSiA steels were enhanced due to the formation of numerous microscale microscope oil pockets on the surface layer and the grain refinement of the surface microstructures, resulting in a significant improvement in wear resistance. With the jet angle of SGP increased from 0° to 90°, the friction coefficient, the wear volume, and the specific wear rate were exhibited to reduce rapidly first, then reduce slowly, and then rise slowly. With the optimal parameters at the jet angle of 60°, compared with the control sample, the average friction coefficient was reduced from 0.2235 to 0.1609, and the wear volume and specific wear rate were reduced from 9.04 × 10⁻³ mm³ to 3.82 × 10⁻³ mm³ and from 15.13 × 10⁻³ mm²/N to 6.36 × 10⁻³ mm²/N, respectively. When the jet angle was 90°, the reduced wear resistance was mainly attributed to the excessive roughness that caused the oil coating on the surface to be severely damaged. Full article

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22 pages, 19176 KiB

Open AccessArticle

Fracture Behavior of Basalt Fiber-Reinforced Airport Pavement Concrete at Different Strain Rates

by Yifan Mu, Haiting Xia, Yong Yan, Zhenhui Wang and Rongxin Guo

Materials 2022, 15(20), 7379; https://doi.org/10.3390/ma15207379 - 21 Oct 2022

Cited by 6 | Viewed by 1390

Abstract

As a commonly used surface structure for airport runways, concrete slabs are subjected to various complex and random loads for a long time, and it is necessary to investigate their fracture performance at different strain rates. In this study, three-point bending fracture tests [...] Read more.

As a commonly used surface structure for airport runways, concrete slabs are subjected to various complex and random loads for a long time, and it is necessary to investigate their fracture performance at different strain rates. In this study, three-point bending fracture tests were conducted using ordinary performance concrete (OPC) and basalt fiber-reinforced airport pavement concrete (BFAPC) with fiber volume contents of 0.2, 0.4, and 0.6%, at five strain rates (10⁻⁶ s⁻¹, 10⁻⁵ s⁻¹, 10⁻⁴ s⁻¹, 10⁻³ s⁻¹, and 10⁻² s⁻¹). Considering parameters such as the peak load, initial cracking load, double K fracture toughness, fracture energy, and critical crack expansion rate, the effects of the fiber volume content and strain rate on the fracture performance of concrete were systematically studied. The results indicate that these fracture parameters of OPC and BFAPC have an obvious strain rate dependence; in particular, the strain rate has a positive linear relationship with peak load and fracture energy, and a positive exponential relationship with the critical crack growth rate. Compared with OPC, the addition of basalt fiber (BF) can improve the fracture performance of airport pavement concrete, to a certain extent, where 0.4% and 0.6% fiber content were the most effective in enhancing the fracture properties of concrete under strain rates of 10⁻⁶–10⁻⁵ s⁻¹ and 10⁻⁴–10⁻² s⁻¹, respectively. From the point of view of the critical crack growth rate, it is shown that the addition of BF can inhibit the crack growth of concrete. In this study, the fracture properties of BFAPC were evaluated at different strain rates, providing an important basis for the application of BFAPC in airport pavement. Full article

(This article belongs to the Special Issue Recent Development in Construction and Building Materials Using Natural and Mineral Fibers)

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18 pages, 4237 KiB

Open AccessArticle

Chemical State of Potassium on the Surface of Iron Oxides: Effects of Potassium Precursor Concentration and Calcination Temperature

by Md. Ariful Hoque, Marcelo I. Guzman, John P. Selegue and Muthu Kumaran Gnanamani

Materials 2022, 15(20), 7378; https://doi.org/10.3390/ma15207378 - 21 Oct 2022

Viewed by 3306

Abstract

Potassium is used extensively as a promoter with iron catalysts in Fisher–Tropsch synthesis, water–gas shift reactions, steam reforming, and alcohol synthesis. In this paper, the identification of potassium chemical states on the surface of iron catalysts is studied to improve our understanding of [...] Read more.

Potassium is used extensively as a promoter with iron catalysts in Fisher–Tropsch synthesis, water–gas shift reactions, steam reforming, and alcohol synthesis. In this paper, the identification of potassium chemical states on the surface of iron catalysts is studied to improve our understanding of the catalytic system. Herein, potassium-doped iron oxide (α-Fe₂O₃) nanomaterials are synthesized under variable calcination temperatures (400–800 °C) using an incipient wetness impregnation method. The synthesis also varies the content of potassium nitrate deposited on superfine iron oxide with a diameter of 3 nm (Nanocat^®) to reach atomic ratios of 100 Fe:x K (x = 0–5). The structure, composition, and properties of the synthesized materials are investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier-transform infrared, Raman spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and X-ray photoelectron spectroscopy, as well as transmission electron microscopy, with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The hematite phase of iron oxide retains its structure up to 700 °C without forming any new mixed phase. For compositions as high as 100 Fe:5 K, potassium nitrate remains stable up to 400 °C, but at 500 °C, it starts to decompose into nitrites and, at only 800 °C, it completely decomposes to potassium oxide (K₂O) and a mixed phase, K₂Fe₂₂O₃₄. The doping of potassium nitrate on the surface of α-Fe₂O₃ provides a new material with potential applications in Fisher–Tropsch catalysis, photocatalysis, and photoelectrochemical processes. Full article

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11 pages, 7593 KiB

Open AccessArticle

Competitive Formation Zones in Carbon Nanotube Float-Catalysis Synthesis: Growth in Length vs. Growth Suppression

by Vladimir Z. Mordkovich, Aida R. Karaeva, Nikita V. Kazennov, Eduard B. Mitberg, Mariem Nasraoui, Boris A. Kulnitskiy and Vladimir D. Blank

Materials 2022, 15(20), 7377; https://doi.org/10.3390/ma15207377 - 21 Oct 2022

Viewed by 1402

Abstract

Catalytic synthesis of carbon nanotubes (CNT) produces numerous various byproducts such as soot, graphite platelets, catalyst nanoparticles, etc. Identification of the byproduct formation mechanisms would help develop routes to more selective synthesis of better carbon-based materials. This work reports on the identification of [...] Read more.

Catalytic synthesis of carbon nanotubes (CNT) produces numerous various byproducts such as soot, graphite platelets, catalyst nanoparticles, etc. Identification of the byproduct formation mechanisms would help develop routes to more selective synthesis of better carbon-based materials. This work reports on the identification of the formation zone and conditions for rather unusual closed multishell carbon nanocapsules in a reactor for float-catalysis synthesis of longer CNT. Structural investigation of the formed nanocapsule material along with computational fluid dynamics (CFD) simulations of the reactor suggested a nanocapsule formation mechanism, in which CNT embryos are suppressed in growth by the in-reactor turbulence. By means of TEM and FFT investigation, it is found that differently oriented single crystals of γ–Fe₂O₃, which do not have clear connections with each other, determine a spherical surface. The carbon atoms that seep through these joints do not form crystalline graphite layers. The resulting additional product in the form of graphene-coated (γ–Fe/Fe₃C)/γ–Fe₂O₃ nanoparticles can be a lightweight and effective microwave absorber. Full article

(This article belongs to the Special Issue Current and Future Trends in Carbon-Based Materials)

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11 pages, 3660 KiB

Open AccessArticle

Evaluation of the Sublimation Process of Some Purine Derivatives: Sublimation Rate, Activation Energy, Mass Transfer Coefficients and Phenomenological Models

by Cerasela-Ionela Cleminte, Daniela Ionita, Cătălin Lisa, Mariana Cristea, Ioan Mamaligă and Gabriela Lisa

Materials 2022, 15(20), 7376; https://doi.org/10.3390/ma15207376 - 21 Oct 2022

Cited by 1 | Viewed by 1238

Abstract

Caffeine and theophylline are compounds with important applications in the pharmaceutical industry and other fields of the chemical industry. These purine derivatives have simple chemical structures, therefore, the evaluation of their sublimation process contributes to the development of mass transfer analysis methods that [...] Read more.

Caffeine and theophylline are compounds with important applications in the pharmaceutical industry and other fields of the chemical industry. These purine derivatives have simple chemical structures, therefore, the evaluation of their sublimation process contributes to the development of mass transfer analysis methods that can later be applied to other compounds with more complex structures. With the help of thermogravimetric analysis in isothermal conditions, the kinetic study of the sublimation of caffeine and theophylline, along with the evaluation of kinetic parameters (activation energy and the pre-exponential factor), was carried out. Global mass transfer coefficients were determined, which vary for caffeine between 53 × 10⁻⁸ and 631 × 10⁻⁸ mol/s·m²·Pa, and for theophylline between 68 × 10⁻⁸ and 441 × 10⁻⁸ mol/s·m²·Pa. The dimensionless equations of the form:

Sh = a + b \cdot {Re}^{c} \cdot {Sc}^{d}

have been proposed, which allow the determination of individual mass transfer coefficients at temperatures between 130 and 160 °C for caffeine and between 170 and 200 °C for theophylline. Full article

(This article belongs to the Section Materials Chemistry)

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