Materials

21 pages, 28625 KiB

Open AccessArticle

Six New Unsymmetrical Imino-1,8-naphthalimide Derivatives Substituted at 3-C Position—Photophysical Investigations

by Sonia Kotowicz, Mateusz Korzec, Jan Grzegorz Małecki, Sylwia Golba, Mariola Siwy, Sebastian Maćkowski and Ewa Schab-Balcerzak

Materials 2022, 15(19), 7043; https://doi.org/10.3390/ma15197043 - 10 Oct 2022

Cited by 1 | Viewed by 1808

Abstract

In this research, six novel unsymmetrical imino-1,8-naphthalimides (AzNI) were synthesized. Comprehensive thermal (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), optical (UV-Vis, photoluminescence), and electrochemical (CV, DPV) studies were carried out to characterize these new compounds. The molecules showed the onset of thermal [...] Read more.

In this research, six novel unsymmetrical imino-1,8-naphthalimides (AzNI) were synthesized. Comprehensive thermal (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), optical (UV-Vis, photoluminescence), and electrochemical (CV, DPV) studies were carried out to characterize these new compounds. The molecules showed the onset of thermal decomposition in the temperature range 283–372 °C and molecular glass behavior. Imino-1,8-naphthalimides underwent reduction and oxidation processes with the electrochemical energy band gap (E_g) below 2.41 eV. The optical properties were evaluated in solvents with different polarities and in the solid-state as a thin films and binary blends with poly(N-vinylcarbazole): (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PVK:PBD). Presented compounds emitted blue light in the solutions and in the green or violet spectral range in the solid-state. Their ability to emit light under external voltage was examined. The devices with guest-host structure emitted light with the maximum located in the blue to red spectral range of the electroluminescence band (EL) depending on the content of the AzNI in the PVK:PBD matrix (guest-host structure). Full article

(This article belongs to the Section Electronic Materials)

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17 pages, 7637 KiB

Open AccessArticle

Mechanical Properties and Constitutive Model of the Cement-Improved Loess under Freeze-Thaw Conditions

by Yaqiang Niu, Luzheng Hou, Zipeng Qin, Xu Wang, Yongfu Zhang, Weilong Shao, Guangrong Jiang, Xianding Guo and Junsuo Zhang

Materials 2022, 15(19), 7042; https://doi.org/10.3390/ma15197042 - 10 Oct 2022

Cited by 1 | Viewed by 1197

Abstract

Cement-improved loess (CIL) is used as a common filler for subgrade construction projects in loess areas. The freeze-thaw (F-T) conditions have a significant effect on the stability of cement-improved loess subgrades in seasonally frozen regions. In this paper, the CIL samples, experiencing different [...] Read more.

Cement-improved loess (CIL) is used as a common filler for subgrade construction projects in loess areas. The freeze-thaw (F-T) conditions have a significant effect on the stability of cement-improved loess subgrades in seasonally frozen regions. In this paper, the CIL samples, experiencing different numbers of F-T cycles at varying freezing temperatures, were used in consolidated undrained triaxial compression tests to investigate the effect of F-T conditions on the mechanical properties of CIL. The results show the stress-strain curves of CIL are of a strain-softening type with strong elastic brittleness. The initial tangent modulus of CIL increases with the growing confining pressure and gradually decreases with the increase in the F-T cycle number and the decreasing freezing temperature. It loses 46.4% of its original value after the twelfth F-T cycle with the confining pressure of 150 kPa and at the freezing temperature of −15 °C. The strength of CIL decreases with the increasing F-T cycle number, but it gradually tends to keep stable after the sixth F-T cycle. The strength also decreases with the reduction in the freezing temperature. It loses 37.7% of its original value after the twelfth F-T cycle with the confining pressure of 150 kPa and the freezing temperature of −15 °C. To express the nonlinearity correlation between the strength and confining pressure under F-T conditions, the Weibull function was applied and a nonlinear Mohr-Coulomb strength criterion was proposed. Through introducing a breakage rate function and a local strain coefficient, a binary-medium constitutive model consisting of bonded elements (soil-particle cohesion) and frictional elements (soil particles or soil aggregations) was established to describe the stress-strain relationships of CIL under F-T conditions. The test results indicated that the model can well describe the strain-softening phenomenon of the stress-strain curve of CIL and reflect the breakage mechanism of CIL. Full article

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12 pages, 6875 KiB

Open AccessArticle

Modeling of Electrical Conductivity for Polymer–Carbon Nanofiber Systems

by Sajad Khalil Arjmandi, Jafar Khademzadeh Yeganeh, Yasser Zare and Kyong Yop Rhee

Materials 2022, 15(19), 7041; https://doi.org/10.3390/ma15197041 - 10 Oct 2022

Cited by 6 | Viewed by 1509

Abstract

There is not a simple model for predicting the electrical conductivity of carbon nanofiber (CNF)–polymer composites. In this manuscript, a model is proposed to predict the conductivity of CNF-filled composites. The developed model assumes the roles of CNF volume fraction, CNF dimensions, percolation [...] Read more.

There is not a simple model for predicting the electrical conductivity of carbon nanofiber (CNF)–polymer composites. In this manuscript, a model is proposed to predict the conductivity of CNF-filled composites. The developed model assumes the roles of CNF volume fraction, CNF dimensions, percolation onset, interphase thickness, CNF waviness, tunneling length among nanoparticles, and the fraction of the networked CNF. The outputs of the developed model correctly agree with the experimentally measured conductivity of several samples. Additionally, parametric analyses confirm the acceptable impacts of main factors on the conductivity of composites. A higher conductivity is achieved by smaller waviness and lower radius of CNFs, lower percolation onset, less tunnel distance, and higher levels of interphase depth and fraction of percolated CNFs in the nanocomposite. The maximum conductivity is obtained at 2.37 S/m by the highest volume fraction and length of CNFs. Full article

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10 pages, 2593 KiB

Open AccessArticle

Effect of NaCl Solution and Simulated Concrete Pore Solution Environment on the Efficiency of Steel Bar Energized Corrosion

by Yang Jianyu, Ye Xin, Jiang Cong and Yang Weijun

Materials 2022, 15(19), 7040; https://doi.org/10.3390/ma15197040 - 10 Oct 2022

Cited by 1 | Viewed by 1302

Abstract

As the main problem of the durability deterioration of concrete structures, the corrosion of steel bars is usually made by the method of electrified corrosion with a short cycle and low cost. However, there is a big difference between the actual corrosion depth [...] Read more.

As the main problem of the durability deterioration of concrete structures, the corrosion of steel bars is usually made by the method of electrified corrosion with a short cycle and low cost. However, there is a big difference between the actual corrosion depth and the theoretical corrosion depth after the reinforcement is electrified. In this paper, through the accelerated corrosion test of steel bars, the change law and influence factors of corrosion efficiency of steel bars in concrete simulated pore solution and NaCl solution are studied. The test results show that the corrosion efficiency of reinforcement in the NaCl solution is higher than that in the concrete simulated pore solution, and the corrosion efficiency in the NaCl solution changes in two stages with the corrosion degree of reinforcement. The corrosion efficiency of concrete in the simulated pore solution decreases with the increase of corrosion degree of reinforcement, which is more significant than that in the NaCl solution. Under the same conditions, the corrosion efficiency is higher in the chloride ion solution with high concentration, and the influence of chloride ion concentration change in the simulated pore solution of concrete on the corrosion efficiency is more significant. The corrosion efficiency of reinforcement under low current density is higher than that under high current density. Full article

(This article belongs to the Special Issue Concrete Durability: Deterioration Mechanisms, Prediction and Rehabilitation)

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15 pages, 26301 KiB

Open AccessArticle

Study of Material Color Influences on Mechanical Characteristics of Fused Deposition Modeling Parts

by Ge Gao, Fan Xu, Jiangmin Xu and Zhenyu Liu

Materials 2022, 15(19), 7039; https://doi.org/10.3390/ma15197039 - 10 Oct 2022

Cited by 6 | Viewed by 2282

Abstract

The objective of the present work is to evaluate the influence of material color on mechanical properties of fused deposition modeling (FDM) parts. The performance of the products is evaluated by testing eight different colors of acrylonitrile butadiene styrene (ABS) and polylactic acid [...] Read more.

The objective of the present work is to evaluate the influence of material color on mechanical properties of fused deposition modeling (FDM) parts. The performance of the products is evaluated by testing eight different colors of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) material in terms of tensile strength, compressive strength, and flexural strength. The analysis of data shows a significant difference in mechanical characteristics of prints depending on filament color. For different colors, these three strengths almost follow the same rising and falling tendency. In order to explore the relationship between mechanical strengths and filament colors, the color-mixing theory and the least-squares method are adopted to fit the best ratio coefficients of different color combinations. Results are presented showing that the strength value (e.g., tensile) of the mixed color can be evaluated through that of primary colors by fitting the other strength (e.g., compressive or flexural). It is shown that the predicted value is always no more than 7% error compared with the actual strength, in spite of two-color or three-color mixtures. An additional confirmation test with seven colored PLA filaments from different suppliers was conducted to focus on the extensibility. The outcomes show the maximum fitting errors of strengths for mixed colors in all cases are within 5%, proving the effectiveness and applicability of this predicted approach. This study can bring a detailed analysis that enables better estimation of the function of material color and contributes to improving the property of FDM printed products for consumers by choosing the suitable filament color. Full article

(This article belongs to the Special Issue Recent Advances in Color 3D Printing)

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7 pages, 975 KiB

Open AccessArticle

Generation of 99.8 fs, 25 kW Peak-Power, Dispersion-Managed Pulses Directly from an Yb-Doped Figure-of-9 Fiber Laser

by Shuai Yuan, Lu Si, Jianing Chen, Junyu Chen and Han Yu

Materials 2022, 15(19), 7038; https://doi.org/10.3390/ma15197038 - 10 Oct 2022

Cited by 1 | Viewed by 1537

Abstract

We reported on the generation of 99.8 fs, 25 kW peak-power, dispersion-managed pulses directly from a passively mode-locked Yb-fiber laser oscillator with a figure-of-9 configuration. The introduction of strongly injected pump power and optical components with a high damage threshold enables high-power operation, [...] Read more.

We reported on the generation of 99.8 fs, 25 kW peak-power, dispersion-managed pulses directly from a passively mode-locked Yb-fiber laser oscillator with a figure-of-9 configuration. The introduction of strongly injected pump power and optical components with a high damage threshold enables high-power operation, while the polarization-maintaining (PM) fiber supports environmentally stable self-started mode-locking. Mode-locking in the soliton-like and negative-dispersion regime is characterized by the dispersion management via tuning the separation distances between a pair of gratings inside the cavity. The oscillator generates stable pulses with up to 40.10 mW average power at a 16.03 MHz repetition rate, corresponding to a pulse energy of 2.5 nJ. To the best of our knowledge, it is the highest peak-power directly obtained by a laser oscillator with a figure-of-9 configuration. Full article

(This article belongs to the Special Issue Fiber Lasers and Non-Linear Optics of Materials)

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11 pages, 2815 KiB

Open AccessArticle

Label Noise Learning Method for Metallographic Image Recognition of Heat-Resistant Steel for Use in Pressure Equipment

by Zhiyuan Shen, Haijun Hu, Ziyi Huang, Yu Zhang, Yafei Wang and Xiufeng Li

Materials 2022, 15(19), 7037; https://doi.org/10.3390/ma15197037 - 10 Oct 2022

Cited by 2 | Viewed by 1325

Abstract

In metallographic examination, spherular pearlite gradation, an important step in a metallographic examination, is the main indicator used to assess the reliability of heat-resistant steel. Recognition of pearlite spheroidization via the manual way mainly depends on the subjective perceptions and experience of each [...] Read more.

In metallographic examination, spherular pearlite gradation, an important step in a metallographic examination, is the main indicator used to assess the reliability of heat-resistant steel. Recognition of pearlite spheroidization via the manual way mainly depends on the subjective perceptions and experience of each inspector. Deep learning-based methods can eliminate the effects of the subjective factors that affect manual recognition. However, images with incorrect labels, known as noisy images, challenge successful application of image recognition of deep learning models to spherular pearlite gradation. A deep-learning-based label noise method for metallographic image recognition is thus proposed to solve this problem. We use a filtering process to pretreat the raw datasets and append a retraining process for deep learning models. The presented method was applied to image recognition for spherular pearlite gradation on a metallographic image dataset which contains 422 images. Meanwhile, three classic deep learning models were also used for image recognition, individually and coupled with the proposed method. Results showed that accuracy of image recognition by a deep learning model solely is lower than the one coupled with our method. Particularly, accuracy of ResNet18 was improved from 72.27% to 77.01%. Full article

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23 pages, 3350 KiB

Open AccessReview

Iron Oxide-Au Magneto-Plasmonic Heterostructures: Advances in Their Eco-Friendly Synthesis

by Marta Miola, Cristina Multari and Enrica Vernè

Materials 2022, 15(19), 7036; https://doi.org/10.3390/ma15197036 - 10 Oct 2022

Cited by 1 | Viewed by 1556

Abstract

In recent years, nanotechnologies have attracted considerable interest, especially in the biomedical field. Among the most investigated particles, magnetic based on iron oxides and Au nanoparticles gained huge interest for their magnetic and plasmonic properties, respectively. These nanoparticles are usually produced starting from [...] Read more.

In recent years, nanotechnologies have attracted considerable interest, especially in the biomedical field. Among the most investigated particles, magnetic based on iron oxides and Au nanoparticles gained huge interest for their magnetic and plasmonic properties, respectively. These nanoparticles are usually produced starting from processes and reagents that can be the cause of potential human health and environmental concerns. For this reason, there is a need to develop simple, green, low-cost, and non-toxic synthesis methods and reagents. This review aims at providing an overview of the most recently developed processes to produce iron oxide magnetic nanoparticles, Au nanoparticles, and their magneto-plasmonic heterostructures using eco-friendly approaches, focusing the attention on the microorganisms and plant-assisted syntheses and showing the first results of the development of magneto-plasmonic heterostructures. Full article

(This article belongs to the Section Biomaterials)

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17 pages, 7457 KiB

Open AccessArticle

Numerical Simulation of Failure Behavior of Brittle Heterogeneous Rock under Uniaxial Compression Test

by Jia Liu, Fengshan Ma, Jie Guo, Tongtong Zhou, Yewei Song and Fangrui Li

Materials 2022, 15(19), 7035; https://doi.org/10.3390/ma15197035 - 10 Oct 2022

Cited by 4 | Viewed by 1340

Abstract

Rocks have formed heterogeneous characteristics after experiencing complex natural geological processes. Studying the heterogeneity of rocks is significant for rock mechanics. In this study, a linear parallel bond model with Weibull distribution in two-dimensional particle flow code (PFC2D) is adopted to study the [...] Read more.

Rocks have formed heterogeneous characteristics after experiencing complex natural geological processes. Studying the heterogeneity of rocks is significant for rock mechanics. In this study, a linear parallel bond model with Weibull distribution in two-dimensional particle flow code (PFC2D) is adopted to study the mechanical characteristics and brittle failure mode of granite rock specimens with different heterogeneity. Firstly, we selected several combinations of key micro-parameters of the parallel bond model. Then, we subjected them to a Weibull distribution to satisfy heterogeneity, respectively. Finally, we chose one optimal combination plan after comparing the stress–strain curves of heterogeneous rock specimens. We analyzed the simulated results of heterogeneous rock specimens. The crack distribution of rock specimens under peak stress shows different characteristics: a diagonal shape in rock specimens with low heterogeneity indexes, or a rotated “y” shape in rock specimens with high heterogeneity indexes. As for failure mode, the numerical simulation results show high consistency with the laboratory experiment results. The rock specimen breaks down almost diagonally, and the whole specimen tends to form an x-shaped conjugate shear failure or the well-known “hour-glass” failure mode. With the increase of the homogeneity index of the rock specimen, the shear rupture angle becomes larger and larger. Generally, the crack number increases with time, and when the rock specimen reaches the peak failure point, the number of cracks increases sharply. The development of cracks in numerical rock specimens under compression test is a result of the coalescence of many microscopic cracks. Furthermore, tensile cracks formed initially, followed by shear behavior along the macroscopic crack plane. We also preliminarily study the mechanical characteristics of heterogeneous rock specimens with discontinuous structural planes. The discontinuous structural planes are simulated by the smooth-joint model. We can conclude that the discontinuous structural planes and the microscopic structural planes which contribute to the heterogeneity have a mutual influence on each other. Full article

(This article belongs to the Special Issue Relations between Structure, Micro- and Nanomechanical Properties of Materials)

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16 pages, 11147 KiB

Open AccessArticle

Investigation of Biaxial Properties of CFRP with the Novel-Designed Cruciform Specimens

by Xiaowen Zhang, Haiyang Zhu, Zhixing Lv, Xiangrun Zhao, Junwei Wang and Qi Wang

Materials 2022, 15(19), 7034; https://doi.org/10.3390/ma15197034 - 10 Oct 2022

Cited by 3 | Viewed by 1221

Abstract

The biaxial loading properties of carbon-fiber-reinforced polymer (CFRP) are critical for evaluating the performance of composite structures under the complex stress state. There are currently no standardized specimens for the CFRP biaxial experiments. This work developed a new design criterion for the cruciform [...] Read more.

The biaxial loading properties of carbon-fiber-reinforced polymer (CFRP) are critical for evaluating the performance of composite structures under the complex stress state. There are currently no standardized specimens for the CFRP biaxial experiments. This work developed a new design criterion for the cruciform specimen coupled with the Hashin criterion. The finite element analysis was conducted to investigate the effect of geometric parameters on the stress distribution in the test area. The embedded continuous laying method (ECLM) was proposed to achieve the thinning of the center of the test region without introducing defects. The manufacturing quality of the cruciform specimens was verified by the ultrasonic C-scanning test. The biaxial test platform consisting of the biaxial loading system, digital image correlation (DIC) system, strain electrical measurement system, and acoustic emission detection system was constructed. The biaxial tensile tests under different biaxial loading ratios were conducted. The results showed that the biaxial failure efficiently occurred in the test area of the cruciform specimens designed and manufactured in this paper. The failure modes and morphology were characterized using macro/microscopic experimental techniques. The biaxial failure envelope was obtained. The results can be used to guide the design of composite structures under biaxial stress. Full article

(This article belongs to the Section Advanced Composites)

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30 pages, 13101 KiB

Open AccessArticle

Electrode Layout Optimization and Numerical Simulation of Cast Conductive Asphalt Concrete Steel Bridge Deck Pavement

by Zhenxia Li, Tengteng Guo, Yuanzhao Chen, Wenping Yang, Shengquan Ding, Menghui Hao, Xu Zhao and Jinyuan Liu

Materials 2022, 15(19), 7033; https://doi.org/10.3390/ma15197033 - 10 Oct 2022

Cited by 2 | Viewed by 1102

Abstract

In order to obtain the optimal electrode layout and ice melting effect of cast conductive asphalt concrete steel bridge deck pavement, firstly, pouring conductive asphalt concrete was prepared; secondly, different electrode materials and layout methods were selected to test the heating rate of [...] Read more.

In order to obtain the optimal electrode layout and ice melting effect of cast conductive asphalt concrete steel bridge deck pavement, firstly, pouring conductive asphalt concrete was prepared; secondly, different electrode materials and layout methods were selected to test the heating rate of the specimen from start to 120 min, and the electrode materials and layout methods were optimized. Then, the finite element analysis software ANSYS was used to build the model for heating and ice melting simulation, and the indoor test was used to further verify the ice melting effect of the cast conductive asphalt coagulation with or without the insulation layer. Finally, the thermal-structural coupling analysis of cast conductive asphalt concrete steel bridge deck pavement was carried out using ANSYS finite element software. The results showed that the stainless steel electrode material had the best heating effect, and the electrode thickness in the range of 0.1~3 mm had no effect on the heating effect. The intermediate heating rate of the upper surface of the stainless steel sheet electrode cast conductive asphalt concrete in the left and right external electrodes was 8

^{\circ}

C/h, while the intermediate heating rate of the upper surface of the stainless steel mesh electrode cast conductive asphalt concrete was 12.9

^{\circ}

C/h. The layout of the left and right buried stainless steel metal mesh was able to effectively improve the snow melting efficiency; ANSYS finite element ice melting simulation was used to obtain the variation law of ice melting efficiency and a temperature field of cast conductive asphalt concrete. The indoor ice melting test showed that when melting the same thickness ice layer at 50 V voltage, it took 240 min with an insulation layer and 720 min without an insulation layer, which was three times that of the ice with an insulation layer, which further verifies the superiority of its ice melting effect. The most unfavorable load position of pavement under load and temperature field was determined. The maximum tensile stress and compressive stress of the pavement surface were transverse, and the maximum shear stress of the pavement bottom was transverse. Full article

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19 pages, 4325 KiB

Open AccessArticle

Elastic Properties of Jute Fiber Reinforced Polymer Composites with Different Hierarchical Structures

by Phani Prasanthi, Sivaji Babu Kondapalli, Niranjan Kumar Sita Rama Morampudi, Venkata Venu Madhav Vallabhaneni, Kuldeep Kumar Saxena, Kahtan Adnan Mohammed, Emanoil Linul, Chander Prakash and Dharam Buddhi

Materials 2022, 15(19), 7032; https://doi.org/10.3390/ma15197032 - 10 Oct 2022

Cited by 7 | Viewed by 1458

Abstract

A two-stage micromechanics technique is used to predict the elastic modulus, as well as the major and minor Poisson’s ratio of unidirectional natural fiber (NF) reinforced composites. The actual NF microstructure consists of cellulose, hemicellulose, lignin, lumen, etc., and these constituents and their [...] Read more.

A two-stage micromechanics technique is used to predict the elastic modulus, as well as the major and minor Poisson’s ratio of unidirectional natural fiber (NF) reinforced composites. The actual NF microstructure consists of cellulose, hemicellulose, lignin, lumen, etc., and these constituents and their contributions are neglected in classical models while quantifying their mechanical properties. The present paper addresses the effect of the real microstructure of the natural jute fiber (JF) by applying a micromechanics approach with the Finite Element Method. Six different hierarchically micro-structured JFs are considered to quantify the JF elastic properties in the first level of homogenization. Later, the JF reinforced polypropylene matrix properties are investigated in the second stage by adopting a homogenization approach. Taking into account the different hierarchical structures (HS), the fiber direction modulus (E₁), transverse modulus (E₂ and E₃), in-plane and out-of-plane shear modulus (G₁₂ and G₂₃), and major (ν₁₂, ν₁₃) and minor (ν₂₃, ν₂₁) Poisson’s ratios are estimated for JF and JF reinforced polypropylene composites. The predicted elastic modulus from micromechanics models is validated against the analytical results and experimental predictions. From the present work, it is observed that the HS of NF needs to be considered while addressing the elastic properties of the NF-reinforced composite for their effective design, particularly at a higher volume fraction of NF. Full article

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12 pages, 5757 KiB

Open AccessArticle

Multifunctional Coding-Feeding Metasurface Based on Phase Manipulation

by Guo-Shuai Huang, Si-Jia Li, Zhuo-Yue Li, Xiao-Bin Liu, Cheng-Yuan He, Huan-Huan Yang and Xiang-Yu Cao

Materials 2022, 15(19), 7031; https://doi.org/10.3390/ma15197031 - 10 Oct 2022

Cited by 4 | Viewed by 1369

Abstract

Multiple functionalities on a shared aperture are crucial for metasurfaces (MSs) in many applications. In this paper, we propose a coding-feeding metasurface (CFMS) with the multiple functions of high-gain radiation, orbital angular momentum (OAM) generation, and radar cross-section (RCS) reduction based on phase [...] Read more.

Multiple functionalities on a shared aperture are crucial for metasurfaces (MSs) in many applications. In this paper, we propose a coding-feeding metasurface (CFMS) with the multiple functions of high-gain radiation, orbital angular momentum (OAM) generation, and radar cross-section (RCS) reduction based on phase manipulation. The unit cell of the CFMS is composed of a rectangular emission patch and two quasi-Minkowski patches for reflective phase manipulation, which are on a shared aperture. The high-gain radiation and multiple modes of ±1, ±2, and ±3 OAM generation were realized by rationally setting the elements and the phase of their excitation. The CFMS presents a broadband RCS reduction of 8 dB from 3.18 GHz to 7.56 GHz for y-polarization and dual-band RCS reduction for x-polarization based on phase interference. To validate the concept of the CFMS, a prototype was fabricated and measured. The results of the measurement agree well with the simulation. A CFMS with the advantages of light weight and low profile has potential application in detection and wireless communication systems for stealth aircraft. Full article

(This article belongs to the Special Issue Metamaterials and Metasurfaces: Fundamentals and Applications)

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14 pages, 3781 KiB

Open AccessArticle

A Simulation Methodology for Analyzing the Energy-Absorption Capabilities of Nanofluidic-System-Filled Tube under Split Hopkinson Pressure Bar Experiment

by Shuming Zhang, Ziqian Zhu, Shuaijun Li, Fei Yu, Chunping Tian and Lu Yao

Materials 2022, 15(19), 7030; https://doi.org/10.3390/ma15197030 - 10 Oct 2022

Cited by 2 | Viewed by 1124

Abstract

The energy-absorption mechanism of nanofluidic systems is being investigated under dynamic cases, represented by the split Hopkinson pressure bar experiment. However, the cost of this cannot be ignored. Therefore, numerical simulation is playing an increasingly important role in optimizing the split Hopkinson pressure [...] Read more.

The energy-absorption mechanism of nanofluidic systems is being investigated under dynamic cases, represented by the split Hopkinson pressure bar experiment. However, the cost of this cannot be ignored. Therefore, numerical simulation is playing an increasingly important role in optimizing the split Hopkinson pressure bar experimental technology and analyzing its accuracy. In this paper, a three-dimensional finite element simulation model of the split Hopkinson pressure bar experimental devices was proposed to analyze the energy-absorption capabilities of nanofluidic-system-filled tubes. The reliability of this methodology was discussed in terms of model construction, model validation and potential application, indicating the simulation methodology is applicable to further investigation and can provide a reference for engineering practice. The simulation results showed that the infiltration pressure and the mass ratio of solid to liquid determine the post-buckling compression stress and the effective compression stroke, respectively. Full article

(This article belongs to the Special Issue Synthesis, Characterization, Theoretical Studies and Application of Nanofluids)

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24 pages, 6274 KiB

Open AccessArticle

The Impact Resistance and Mechanical Properties of Recycled Aggregate Concrete with Hooked-End and Crimped Steel Fiber

by Xiangqing Kong, Yanbin Yao, Bojian Wu, Wenjiao Zhang, Wenchang He and Ying Fu

Materials 2022, 15(19), 7029; https://doi.org/10.3390/ma15197029 - 10 Oct 2022

Cited by 8 | Viewed by 1607

Abstract

The utilization of recycled coarse aggregate (RCA) from construction and demolition waste (CDW) is a sustainable solution to protect the fragile natural environment and save the diminishing natural resources. The current study was aimed at exploring the impact resistance and mechanical properties of [...] Read more.

The utilization of recycled coarse aggregate (RCA) from construction and demolition waste (CDW) is a sustainable solution to protect the fragile natural environment and save the diminishing natural resources. The current study was aimed at exploring the impact resistance and mechanical properties of recycled aggregate concrete (RAC) affected by hooked-end steel fiber (HF) and crimped steel fiber (CF). Fifteen concrete mixtures considering different RCA substitution ratio, steel fiber dosage, and steel fiber shapes were designed. Meanwhile, a statistical analysis method-based Weibull distribution was introduced to evaluate the variations of impact test results, presented using a reliability function. Lastly, the microstructural morphologies of interfacial transition zones at the cement paste/aggregate and cement paste/fiber interfaces were observed using a scanning electron microscope (SEM). The experimental results showed that the impact resistance and mechanical properties mildly decreased with the increase in substitution ratio of RCA, whereas they conclusively increased with the increase in steel fiber content. Steel fiber recycled aggregate concrete (SFRAC) with 1.5% steel fiber content had the best impact resistance, and its initial cracking times and final failure times were 3.25–4.75 and 8.78–29.08 times those of plain RAC, respectively. HF has better impact resistance than CF. The SEM observations of microstructures indicated that the hardened cement paste of natural aggregate concrete (NAC) was more compact than that of RAC. Steel fiber had a better connection with the cement paste interface than that of aggregate and cement paste owing to better thermal conductivity. This research could be a guide for SFRAC as a structural material in practical engineering, steering the construction industry toward the circular economy. Full article

(This article belongs to the Special Issue Metal and Polymer Composites for Functional and Structural Applications)

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14 pages, 5817 KiB

Open AccessArticle

Experimental Study on Laser Ablation Texture-Assisted Grinding of Tungsten Alloy

by Bing Chen, Ye Guo, Shunshun Li and Guoyue Liu

Materials 2022, 15(19), 7028; https://doi.org/10.3390/ma15197028 - 10 Oct 2022

Cited by 3 | Viewed by 1307

Abstract

In order to machine the tungsten alloy with high efficiency, low damage and precision, laser ablation texture technology and precision grinding technology were combined to carry out grinding experiments of tungsten alloy and laser ablation texture-assisted grinding experiments. The advantages of laser ablation [...] Read more.

In order to machine the tungsten alloy with high efficiency, low damage and precision, laser ablation texture technology and precision grinding technology were combined to carry out grinding experiments of tungsten alloy and laser ablation texture-assisted grinding experiments. The advantages of laser ablation texture-assisted grinding tungsten alloy were investigated by comparing of the surface morphology, grinding force and surface roughness between ordinary grinding and laser ablative texture-assisted grinding. The results demonstrate that the surface morphology of ordinary grinding tungsten alloy was poor, the surface roughness was relatively high and the grinding force was relatively large. The surface morphology of the laser ablation texture-assisted grinding tungsten alloy processed by laser ablation texture was improved, the surface roughness decreased by 0.023 µm–0.204 µm, the normal force decreased by 49.91–59.46% and the tangent force decreased by 44.11–58.49%. Meantime, for the area ratio of texture A being the most, the grinding effect was related to the area ratio of texture, and the lowest grinding force and the best surface quality were observed on the tungsten alloy with the laser ablated texture A; the grinding forces and roughness of the other textures’ workpiece was similar and close because of their similar area ratios. The results demonstrate that laser ablation texture-assisted grinding of tungsten alloy could improve machining quality and reduce grinding force, which would provide guidance for realizing the high efficiency and precision machining of tungsten alloy. Full article

(This article belongs to the Special Issue New Advances in Coatings and Surface Treatments for Cutting and Grinding Tools)

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9 pages, 4463 KiB

Open AccessArticle

Effect of Single Loading Time to the Cyclic Ablation of C/C-SiC-ZrC Composite

by Wei Feng, Xinyu Wang, Yunlong Tian, Lei Liu and Boyan Li

Materials 2022, 15(19), 7027; https://doi.org/10.3390/ma15197027 - 10 Oct 2022

Cited by 1 | Viewed by 1171

Abstract

To understand the influence of single loading time on the cyclic ablation of carbide modified C/C composites, a C/C-SiC-ZrC composite was impacted by plasma at 2600 K for 50 s under reciprocating 0.5 (C_0.5) and 5 s (C₅), respectively. [...] Read more.

To understand the influence of single loading time on the cyclic ablation of carbide modified C/C composites, a C/C-SiC-ZrC composite was impacted by plasma at 2600 K for 50 s under reciprocating 0.5 (C_0.5) and 5 s (C₅), respectively. The composites displayed similar negative mass and rising positive linear ablation rates from C_0.5 to C₅. Phases, micro-morphologies, and surface temperature analysis suggested that the partially oxidized SiC-ZrC covering on the ablated sample cracked and was persistently peeled off. The mass gain resulted from the ceramic’s protection of the nearby carbon from complete oxidation. The longer single loading of 5 s caused strengthened thermal chemical reaction and mechanical erosion, which resulted in the bigger linear loss. Full article

(This article belongs to the Special Issue Performance Improvement Strategies for Graphene and Carbon Nanotubes-Based Composites)

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13 pages, 5336 KiB

Open AccessArticle

Piezoelectric Nanogenerator Based on Electrospinning PVDF/Cellulose Acetate Composite Membranes for Energy Harvesting

by Yuanyuan Li, Qing Hu, Rui Zhang, Wenmei Ma, Siwei Pan, Yaohong Zhao, Qing Wang and Pengfei Fang

Materials 2022, 15(19), 7026; https://doi.org/10.3390/ma15197026 - 10 Oct 2022

Cited by 10 | Viewed by 2374

Abstract

The organic piezoelectric polymer polyvinylidene fluoride (PVDF) has attracted extensive research because of its excellent flexibility and mechanical energy-harvesting properties. Here, the electrospinning technique was taken to fabricate synthesized fiber membranes of a PVDF/cellulose acetate (CA) composite. The obtained PVDF/CA electrospun fiber membranes [...] Read more.

The organic piezoelectric polymer polyvinylidene fluoride (PVDF) has attracted extensive research because of its excellent flexibility and mechanical energy-harvesting properties. Here, the electrospinning technique was taken to fabricate synthesized fiber membranes of a PVDF/cellulose acetate (CA) composite. The obtained PVDF/CA electrospun fiber membranes (EFMs) were employed to prepare a flexible nanogenerator. XRD and FTIR spectroscopy revealed the enhancement of piezoelectric behavior due to an increase in β-phase in PVDF/CA EFMs compared with cast films. The PVDF/CA fibers (mass ratio of PVDF to CA = 9:1) showed an output voltage of 7.5 V and a short-circuit current of 2.1 μA under mechanical stress of 2 N and frequency of 1 Hz, which were 2.5 and two times greater than those of the pure PVDF fibers, respectively. By charging a 4.7 µF capacitor for 15 min with the voltage generated by the PVDF/CA EFMs, nine LED lamps could be lit. The work provides an effective approach to enhancing the piezoelectric effects of PVDF for low-power electronic loading of macromolecule polymers. Full article

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

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14 pages, 4003 KiB

Open AccessArticle

Cenosphere-Based Zeolite Precursors of Lutetium Encapsulated Aluminosilicate Microspheres for Application in Brachytherapy

by Tatiana Vereshchagina, Ekaterina Kutikhina, Sergei Vereshchagin, Olga Buyko and Alexander Anshits

Materials 2022, 15(19), 7025; https://doi.org/10.3390/ma15197025 - 10 Oct 2022

Cited by 1 | Viewed by 1537

Abstract

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase—95.4; (SiO₂/Al₂O₃)_glass—3.1; (Si/Al)_at. = 2.6) were used to fabricate lutetium-176 encapsulated aluminosilicate microspheres as precursors of radiolabeled microspheres applied for selective irradiation of [...] Read more.

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase—95.4; (SiO₂/Al₂O₃)_glass—3.1; (Si/Al)_at. = 2.6) were used to fabricate lutetium-176 encapsulated aluminosilicate microspheres as precursors of radiolabeled microspheres applied for selective irradiation of tumors. To incorporate Lu³⁺ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (i) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (ii) loading of zeolitized microspheres with Lu³⁺ by means of ion exchange 3Na⁺ ↔ Lu³⁺; (iii) Lu³⁺ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu³⁺ loaded microspheres under thermal treatment at 1273–1473 K. Two types of zeolitized products, such as NaX (FAU) and NaP1 (GIS) bearing microspheres having the specific surface area of 204 and 33 m²/g, accordingly, were prepared and their Lu³⁺ sorption abilities were studied. As revealed, the Lu³⁺ sorption capacities of the zeolitized products are about 130 and 70 mg/g Lu³⁺ for NaX and NaP1 microspheres, respectively. It was found that the long-time heating of the Lu³⁺-loaded zeolite precursors at 1273 K in a fixed bed resulted in the crystallization of monoclinic Lu₂Si₂O₇ in both zeolite systems, which is a major component of crystalline constituents of the calcined microspheres. The fast heating–cooling cycle at 1473 K in a moving bed resulted in the amorphization of zeolite components in both precursors and softening glass crystalline matter of the NaX-bearing precursor with preserving its spherical form and partial elimination of surface open pores. The NaX-bearing microspheres, compared to NaP1-based precursor, are characterized by uneven Lu distribution over the zeolite-derived layer. The precursor based on gismondin-type zeolite provides a near-uniform Lu distribution and acceptable Lu content (up to 15 mol.% Lu₂O₃) in the solid phase. Full article

(This article belongs to the Special Issue Zeolitic Materials: Structure, Properties, and Applications)

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14 pages, 2913 KiB

Open AccessArticle

Comparative Analysis of Lead Removal from Liquid Copper by ICF and CCF Refining Technologies

by Leszek Blacha, Albert Smalcerz, Bartosz Wecki, Jerzy Labaj, Debela Geneti Desisa and Maciej Jodkowski

Materials 2022, 15(19), 7024; https://doi.org/10.3390/ma15197024 - 10 Oct 2022

Viewed by 1128

Abstract

Innovative technologies require the use of materials that meet increasingly high requirements; one such requirement is the purity of metals. In the case of copper, this translates into a parameter related to electrical conductivity. Traditional metal refining technologies have some limitations that can [...] Read more.

Innovative technologies require the use of materials that meet increasingly high requirements; one such requirement is the purity of metals. In the case of copper, this translates into a parameter related to electrical conductivity. Traditional metal refining technologies have some limitations that can be eliminated through the use of modern melting aggregates. Such solutions include vacuum induction furnaces, comprising an induction furnace with a cold crucible. As part of this work, the possibilities of refining copper and lead alloys were investigated. In addition, the research was carried out with the use of two induction vacuum aggregates, allowing us to compare their effectiveness. The tests were carried out in a pressure range of 10–1000 Pa and at temperatures of 1273–1473 K. The results obtained made it possible to determine the mass transport coefficient of lead from an alloy with copper, and to determine the share of resistance in individual stages of the process. For experiments conducted inside an induction crucible furnace, lowering the working pressure inside the furnace chamber from 1000 to 10 Pa while increasing the temperature from 1323 to 1473 K was accompanied by a drop in the lead concentration inside the alloy of 69 to 96%, compared to its initial mass. For experiments conducted inside a cold crucible furnace, approximate values of lead removal appeared for lower temperatures (1273 to 1323 K), confirming that the analyzed process happens faster in this aggregate. Full article

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

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16 pages, 4739 KiB

Open AccessArticle

Preparation of Cemented Carbide and Study of Copper-Accelerated Salt Spray Corrosion and Erosion Behavior

by Shasha Wei, Yuanyou Li, Renxin Wang, Hu Yang, Ziming Guo, Rongchuan Lin, Qingmin Huang and Yuhui Zhou

Materials 2022, 15(19), 7023; https://doi.org/10.3390/ma15197023 - 10 Oct 2022

Viewed by 1355

Abstract

(1) Mud pulser carbide rotors, as a core component of ground communication in crude oil exploration, are often subjected to mud erosion and acid corrosion, resulting in pitting pits on the surface, which affects the accuracy. The purpose of this study was to [...] Read more.

(1) Mud pulser carbide rotors, as a core component of ground communication in crude oil exploration, are often subjected to mud erosion and acid corrosion, resulting in pitting pits on the surface, which affects the accuracy. The purpose of this study was to investigate the acid corrosion and erosion behavior of cemented carbide materials and provide a reference for the wider application of cemented carbide materials in the petrochemical industry. (2) Experimental samples of tungsten–cobalt carbide were sintered at a low pressure by powder metallurgy. The petrochemical application environment was simulated by accelerated salt spray corrosion and solid slurry erosion with the aid of acidic copper, and the experimental phenomena were analyzed by SEM (scanning electron microscope), EDS (Energy Dispersive Spectroscopy), and XRD (X-ray diffraction). (3) The experimental results show that the coercivity of the pitted cobalt-cemented tungsten carbide prepared in this study was 17.89 KA/m, and the magnetic saturation strength was 14.42 G·cm³/g. The corrosion rate was the fastest during the acidic copper acceleration experiments from 4 h to 16 h, and the corrosion products of WCo₃ and Co₃O₄ were generated on the corrosion surface. The maximum erosion rate of 0.00104 in the erosion experiment corresponds to a corrosion sample with a corrosion time of 36 h. (4) Therefore, the coercive magnetic force and magnetic saturation strength could be derived from the prepared carbide hard phase grains and carbon content in the appropriate range. The corrosion product in the corrosion process slowed the corrosion rate, and a large amount of cobalt and a small amount of tungsten was lost by oxidation during the corrosion process. The corrosion time had the greatest effect on the erosion performance of the carbide, and the long corrosion time led to surface sparseness, which reduced the erosion resistance. Full article

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9 pages, 2429 KiB

Open AccessArticle

Investigation on Application Prospect of Refractories for Hydrogen Metallurgy: The Enlightenment from the Reaction between Commercial Brown Corundum and Hydrogen

by Shaofei Li, Ding Chen, Huazhi Gu, Ao Huang and Lvping Fu

Materials 2022, 15(19), 7022; https://doi.org/10.3390/ma15197022 - 10 Oct 2022

Cited by 7 | Viewed by 1665

Abstract

Hydrogenous environments put forward new requirements to refractories for the hydrogen metallurgy field. The temperature and impurities in refractories played an important role in stability. A commercial brown corundum with many impurities was adopted as a raw material, thermodynamic calculations and reduction experiments [...] Read more.

Hydrogenous environments put forward new requirements to refractories for the hydrogen metallurgy field. The temperature and impurities in refractories played an important role in stability. A commercial brown corundum with many impurities was adopted as a raw material, thermodynamic calculations and reduction experiments of the brown corundum by high-purity hydrogen (99.99%) were accepted to investigate the stability of the oxides. The weight loss and mass fraction were tested to estimate the stability of the oxides in the brown corundum. XRD and SEM were used to analyze the mineral compositions and microstructures. The results showed that: the thermodynamic stability of the oxides in the brown corundum under high-purity hydrogen was in the order of Al₂O₃ > CaO > MgO > SiO₂ > TiO₂ > Fe₂O₃ at temperatures lower than 1400 °C. Obvious weight loss appeared after heating at 1400 °C for 8 h. The content of CaO did not decline after reduction even at 1800 °C, owing to the formation of hibonite (CaAl₁₂O₁₉), high-purity Al₂O₃ and CaAl₁₂O₁₉ -based refractories had the prospect for lining materials in the hydrogen metallurgy field, owing to their excellent chemical stability under hydrogenous environments. Full article

(This article belongs to the Section Corrosion)

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16 pages, 6400 KiB

Open AccessArticle

Interfacial Microstructure and Mechanical Properties of 1Cr18Ni9Ti/1Cr21Ni5Ti Stainless Steel Joints Brazed with Mn-Based Brazing Filler

by Lei Chen, Huize Chen, Weipeng Yang, Qinlian Zhang, Bo Yang, Yazhen Hu, Xiaoqing Si, Tong Lin, Jian Cao, Junlei Qi and Chun Li

Materials 2022, 15(19), 7021; https://doi.org/10.3390/ma15197021 - 10 Oct 2022

Cited by 1 | Viewed by 1173

Abstract

The problem of stainless steel brazing is still the focus of scientific research. In this work, the Mn-based brazing filler was used to braze 1Cr18Ni9Ti and 1Cr21Ni5Ti stainless steel. The typical microstructure of the 1Cr18Ni9Ti/1Cr21Ni5Ti joint was analyzed in detail, and the interface [...] Read more.

The problem of stainless steel brazing is still the focus of scientific research. In this work, the Mn-based brazing filler was used to braze 1Cr18Ni9Ti and 1Cr21Ni5Ti stainless steel. The typical microstructure of the 1Cr18Ni9Ti/1Cr21Ni5Ti joint was analyzed in detail, and the interface structure of the joint was determined to be 1Cr18Ni9Ti/Mn(s, s)/1Cr21Ni5Ti. The brazing temperature and holding time were shown to have a great influence on the microstructure of the brazed joint. The tensile strength of brazed joints first increased and then decreased with the rising of the brazing temperature and the holding time. The maximum tensile strength was 566 MPa when the joints were brazed at 1125 °C for 15 min. The diffusion of Mn and Cr was an important factor affecting the quality of the joints. The diffusion distances of Mn and Cr at different brazing temperatures and holding times were measured, and the diffusion activation energy and diffusion coefficient were achieved by the Arrhenius equation. Full article

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18 pages, 9334 KiB

Open AccessArticle

Analysis of Microchannel Heat Sink of Silicon Material with Right Triangular Groove on Sidewall of Passage

by Surojit Saha, Tabish Alam, Md Irfanul Haque Siddiqui, Mukesh Kumar, Masood Ashraf Ali, Naveen Kumar Gupta and Dan Dobrotă

Materials 2022, 15(19), 7020; https://doi.org/10.3390/ma15197020 - 10 Oct 2022

Cited by 8 | Viewed by 1524

Abstract

Microchannel heat sink (MCHS) is a promising solution for removing the excess heat from an electronic component such as a microprocessor, electronic chip, etc. In order to increase the heat removal rate, the design of MCHS plays a vital role, and can avoid [...] Read more.

Microchannel heat sink (MCHS) is a promising solution for removing the excess heat from an electronic component such as a microprocessor, electronic chip, etc. In order to increase the heat removal rate, the design of MCHS plays a vital role, and can avoid damaging heat-sensitive components. Therefore, the passage of the MCHS has been designed with a periodic right triangular groove in the flow passage. The motivation for this form of groove shape is taken from heat transfer enhancement techniques used in solar air heaters. In this paper, a numerical study of this new design of microchannel passage is presented. The microchannel design has five variable groove angles, ranging from 15° to 75°. Computational fluid dynamics (CFD) is used to simulate this unique microchannel. Based on the Navier–Stokes and energy equations, a 3D model of the microchannel heat sink was built, discretized, and laminar numerical solutions for heat transfer, pressure drop, and thermohydraulic performance were derived. It was found that Nusselt number and thermo-hydraulic performance are superior in the microchannel with a 15° groove angle. In addition, thermohydraulic performance parameters (THPP) were evaluated and discussed. THPP values were found to be more than unity for a designed microchannel that had all angles except 75°, which confirm that the proposed design of the microchannel is a viable solution for thermal management. Full article

(This article belongs to the Special Issue Ecodesign for Composite Materials and Products)

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29 pages, 81231 KiB

Open AccessEditor’s ChoiceReview

A Review of the Intelligent Optimization and Decision in Plastic Forming

by Xuefeng Tang, Zhizhou Wang, Lei Deng, Xinyun Wang, Jinchuan Long, Xin Jiang, Junsong Jin and Juchen Xia

Materials 2022, 15(19), 7019; https://doi.org/10.3390/ma15197019 - 10 Oct 2022

Cited by 5 | Viewed by 3141

Abstract

The plastic forming process involves many influencing factors and has some inevitable disturbance factors, rendering the multi-objective collaborative optimization difficult. With the rapid development of big data and artificial intelligence (AI) technology, intelligent process optimization has become one of the critical technologies for [...] Read more.

The plastic forming process involves many influencing factors and has some inevitable disturbance factors, rendering the multi-objective collaborative optimization difficult. With the rapid development of big data and artificial intelligence (AI) technology, intelligent process optimization has become one of the critical technologies for plastic forming. This paper elaborated on the research progress on the intelligent optimization of plastic forming and the data-driven process planning and decision-making system in plastic forming process optimization. The development trend in intelligent optimization of the plastic forming process was researched. This review showed that the intelligent optimization algorithm has great potential in controlling forming quality, microstructure, and performance in plastic forming. It is a general trend to develop an intelligent optimization model of the plastic forming process with high integration, versatility, and high performance. Future research will take the data-driven expert system and digital twin system as the carrier, integrate the optimization algorithm and model, and realize the multi-scale, high-precision, high-efficiency, and real-time optimization of the plastic forming process. Full article

(This article belongs to the Special Issue Feature Papers in "Metals and Alloys" Section)

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7 pages, 3032 KiB

Open AccessArticle

Electrocaloric Effect in Different Oriented BaZr_0.15Ti_0.85O₃ Single Crystals

by Yun Ou, Chihou Lei and Dongliang Shan

Materials 2022, 15(19), 7018; https://doi.org/10.3390/ma15197018 - 10 Oct 2022

Viewed by 1007

Abstract

The electrocaloric effect of ferroelectrics is promising for new solid-state refrigeration. However, the current research on the electrocaloric effect of bulk ferroelectrics mainly focuses on (001) orientation. Thus, we studied the electrocaloric effect of BaZr_0.15Ti_0.85O₃ single crystals with [...] Read more.

The electrocaloric effect of ferroelectrics is promising for new solid-state refrigeration. However, the current research on the electrocaloric effect of bulk ferroelectrics mainly focuses on (001) orientation. Thus, we studied the electrocaloric effect of BaZr_0.15Ti_0.85O₃ single crystals with different orientations through the nonlinear thermodynamic approach and entropy analysis. The results show that the dipolar entropy of (111)-oriented BaZr_0.15Ti_0.85O₃ single crystals exhibits a greater change after applying an external electric field, compared with (001)- and (110)-orientations, and the (001)-oriented electrocaloric responses are consistent with experimental observations. The (111)-oriented BaZr_0.15Ti_0.85O₃ single crystals have a more significant electrocaloric response, resulting in a broader work temperature range with a large electrocaloric effect. These insights offer an alternative way to enhance the electrocaloric response of ferroelectric single crystals. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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15 pages, 1587 KiB

Open AccessArticle

A Long-Term Study on the Content of Polycyclic Aromatic Hydrocarbons in Rubber from End-of-Life Tires of Passenger Cars and Trucks

by Stefan Hoyer, Lothar Kroll, Kirsten Lippert and Albrecht Seidel

Materials 2022, 15(19), 7017; https://doi.org/10.3390/ma15197017 - 10 Oct 2022

Cited by 3 | Viewed by 1509

Abstract

At the European level, limits have been set (REACH) for the content of polycyclic aromatic hydrocarbons (PAH) in products with rubber and plastic components that come into contact with human skin or the oral cavity. These limit values reported in Commission Regulation (EU) [...] Read more.

At the European level, limits have been set (REACH) for the content of polycyclic aromatic hydrocarbons (PAH) in products with rubber and plastic components that come into contact with human skin or the oral cavity. These limit values reported in Commission Regulation (EU) 1272/2013 are of particular importance for the utilization of end-of-life tires (ELT) as recycled rubber materials for consumer applications, but a suitable analytical method has not yet been specified. On the other hand, comprehensive measurement series of the PAH content of ELT materials are scarce in the context of compliance testing against this regulation and general published PAH levels in ELT materials are often based on very different analytical methods. In the present work, the PAH content of three different rubber granulates from ELT (obtained from whole truck and passenger car tires and truck tire treads) were investigated over a period of two years. The Grimmer method was used for PAH profile analysis, which in terms of extraction intensity and sample preparation not only meets the requirements for a reliable determination of the EU priority PAH, but in addition covers a more comprehensive PAH profile. A total of 26 different PAH compounds, including the 8 EU priority PAH (REACH) and the 16 U.S. EPA priority PAH, were analyzed and their variations over time were examined to obtain reliable current data for PAH content in rubber granulates produced from ELT. Full article

(This article belongs to the Special Issue Sustainable Solutions and Challenges towards Polymeric Waste Materials)

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21 pages, 12310 KiB

Open AccessReview

Impact of Corrosion on the Bond Strength between Concrete and Rebar: A Systematic Review

by Amadou Sakhir Syll and Toshiyuki Kanakubo

Materials 2022, 15(19), 7016; https://doi.org/10.3390/ma15197016 - 10 Oct 2022

Cited by 10 | Viewed by 2031

Abstract

Corrosion of the reinforcement affects more than the cross-sectional area of the rebar. The volume of steel also increases due to expansive corrosion products, leading to the cracking, delamination, and spalling of concrete. As a result, the bond capacity between concrete and rebar [...] Read more.

Corrosion of the reinforcement affects more than the cross-sectional area of the rebar. The volume of steel also increases due to expansive corrosion products, leading to the cracking, delamination, and spalling of concrete. As a result, the bond capacity between concrete and rebar is affected. Researchers have extensively examined the impact of corrosion on the bond strength between concrete and rebar to propose empirical, theoretical, or numerical predictive models. Therefore, research programs on this topic have increased rapidly in recent years. This article presents a systematic literature review to explore experimental methods, outcomes, and trends on this topic. The Web of Science search collected 84 relevant research articles through a rigorous selection. Key factors that affect bond strength degradation, including concrete cover, concrete strength, and stirrups, have been documented. However, a general model is still unavailable due to discrepancies caused by differences in testing methods to evaluate the effect of corrosion on bond strength. Furthermore, researchers attempted to clarify the degradation mechanism of bond strength affected by corrosion. As a result, new alternatives have been proposed to build a practical model to assess the bond strength deterioration of corroded structures. Full article

(This article belongs to the Special Issue Mechanical Behavior of Concrete Materials and Structures: Experimental Evidence and Analytical Models (Volume II))

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17 pages, 6309 KiB

Open AccessArticle

Effect of pH on the In Vitro Degradation of Borosilicate Bioactive Glass and Its Modulation by Direct Current Electric Field

by Xuanyu Zhang, Minhui Zhang and Jian Lin

Materials 2022, 15(19), 7015; https://doi.org/10.3390/ma15197015 - 10 Oct 2022

Cited by 3 | Viewed by 1472

Abstract

Controlled ion release and mineralization of bioactive glasses are essential to their applications in bone regeneration. Tuning the chemical composition and surface structure of glasses are the primary means of achieving this goal. However, most bioactive glasses exhibit a non-linear ion release behavior. [...] Read more.

Controlled ion release and mineralization of bioactive glasses are essential to their applications in bone regeneration. Tuning the chemical composition and surface structure of glasses are the primary means of achieving this goal. However, most bioactive glasses exhibit a non-linear ion release behavior. Therefore, modifying the immersion environment of glasses through external stimuli becomes an approach. In this study, the ion release and mineralization properties of a borosilicate bioactive glass were investigated in the Tris buffer and K₂HPO₄ solutions with different pH. The glass had a faster ion release rate at a lower pH, but the overly acidic environment was detrimental to hydroxyapatite production. Using a direct current (DC) electric field as an external stimulus, the pH of the immersion solution could be modulated within a narrow range, thereby modulating ion release from the glass. As a result, significant increases in ion release were observed after three days, and the development of porous mineralization products on the glass surface after six days. This study demonstrates the effectiveness of the DC electric field in modulating the ion release of the bioactive glass in vitro and provides a potential way to regulate the degradation of the glass in vivo. Full article

(This article belongs to the Section Biomaterials)

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15 pages, 28172 KiB

Open AccessArticle

Injection Molding and Sintering of ZrO₂ Ceramic Powder Modified by a Zirconate Coupling Agent

by Qiangyi Mao, Liang Qiao, Jingwu Zheng, Yao Ying, Jing Yu, Wangchang Li, Shenglei Che and Wei Cai

Materials 2022, 15(19), 7014; https://doi.org/10.3390/ma15197014 - 10 Oct 2022

Cited by 2 | Viewed by 1571

Abstract

Ceramic injection molding is a near-net shape-processing technique, producing ceramic components with low tooling costs and complex shapes. In this paper, ZrO₂ ceramics with high loading content in the green part were prepared by powder modification using zirconate coupling agent, injection molding [...] Read more.

Ceramic injection molding is a near-net shape-processing technique, producing ceramic components with low tooling costs and complex shapes. In this paper, ZrO₂ ceramics with high loading content in the green part were prepared by powder modification using zirconate coupling agent, injection molding and sintering, which benefited decreasing the usage of binders and deformation of ceramics. The rheological characteristics of feedstocks, densities, microstructures and mechanical properties of green and sintered parts with the different coupling media and sintering temperatures were studied. The results showed that the addition of a zirconate coupling agent with ethanol medium obviously increased the flowability of feedstocks and benefited achieving the green parts with high powder loading (86.5 wt.%) and bending strength (12.9 MPa) and the final unbroken ceramics. In addition, the sintering temperatures from 1500–1575 °C had no significant effects on the density, hardness, and surface morphology of the ceramic samples. However, the bending strength increased and some large grains with transgranular fracture occurred on the fractural surface at the sintering temperature of 1575 °C. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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