Materials

16 pages, 4478 KiB

Open AccessArticle

Activated Carbon and Clay Pellets Coated with Hydroxyapatite for Heavy Metal Removal: Characterization, Adsorption, and Regeneration

by Inga Jurgelane and Janis Locs

Materials 2023, 16(9), 3605; https://doi.org/10.3390/ma16093605 - 08 May 2023

Cited by 3 | Viewed by 1660

Abstract

In the present work, activated-carbon-containing pellets were preparedby direct chemical activation of sawdust, using clays as a binder. The obtained pellets (ACC) were coated with hydroxyapatite (HAp) nanoparticles (ACC-HAp) to improve adsorption towards Pb(II), Cu(II), Zn(II), and Ni(II). The pellets were characterized by [...] Read more.

In the present work, activated-carbon-containing pellets were preparedby direct chemical activation of sawdust, using clays as a binder. The obtained pellets (ACC) were coated with hydroxyapatite (HAp) nanoparticles (ACC-HAp) to improve adsorption towards Pb(II), Cu(II), Zn(II), and Ni(II). The pellets were characterized by scanning electron microscopy (SEM), by Fourier transform infrared spectroscopy (FTIR), and with a gas sorptometer. The effect of pH, contact time, and initial concentration on adsorption performance was investigated. Additionally, desorption studies were performed, and the regeneration influence on compressive strength and repeated Pb(II) adsorption was investigated. The results showed that, after coating ACC pellets with HAp nanoparticles, the adsorption capacity increased for all applied heavy metal ions. Pb(II) was adsorbed the most, and the best results were achieved at pH 6. The adsorption process followed the pseudo-second-order kinetic model. The adsorption isotherm of Pb(II) is better fitted to the Langmuir model, showing the maximum adsorption capacity of 56 and 47 mg/g by ACC-HAp and ACC pellets, respectively. The desorption efficiency of Pb(II)-loaded ACC-HAp pellets increased by lowering the pH of the acid, resulting in the dissolution of the HAp coating. The best desorption results were achieved with HCl at pH 1 and 1.5. Therefore, the regeneration procedure consisted of desorption, rinsing with distilled water, and re-coating with HAp nanoparticles. After the regeneration process, the Pb(II) adsorption was not affected. However, the desorption stage within the regeneration process decreased the compressive strength of the pellets. Full article

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19 pages, 7755 KiB

Open AccessArticle

Study on Mass Erosion and Surface Temperature during High-Speed Penetration of Concrete by Projectile Considering Heat Conduction and Thermal Softening

by Kai Dong, Kun Jiang, Chunlei Jiang, Hao Wang and Ling Tao

Materials 2023, 16(9), 3604; https://doi.org/10.3390/ma16093604 - 08 May 2023

Cited by 2 | Viewed by 993

Abstract

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass [...] Read more.

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass loss. In this paper, theoretical models are established to calculate the mass erosion and heat conduction of projectile noses, including models of cutting, melting, the heat conduction of flash temperature, and the conversion of plastic work into heat. The friction cutting model is modified considering the heat softening of metal, and a model of non-adiabatic processes for the nose was established based on the heat conduction theory to calculate the surface temperature. The coupling numerical calculation of the erosion and heat conduction of the projectile nose shows that melting erosion is the main factor of mass loss at high-speed penetration, and the mass erosion ratio of melting and cutting is related to the initial velocity. Critical velocity without melting erosion and a constant ratio of melting and cutting erosion exists, and the critical velocities are closely related to the melting temperature. In the process of penetration, the thickness of the heat affected zone (HAZ) gradually increases, and the entire heat conduction zone (EHZ) is about 5~6 times the thickness of the HAZ. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)

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19 pages, 4104 KiB

Open AccessReview

Sensors Based on Auxetic Materials and Structures: A Review

by Shanshan Dong and Hong Hu

Materials 2023, 16(9), 3603; https://doi.org/10.3390/ma16093603 - 08 May 2023

Cited by 2 | Viewed by 4200

Abstract

Auxetic materials exhibit a negative Poisson’s ratio under tension or compression, and such counter-intuitive behavior leads to enhanced mechanical properties such as shear resistance, impact resistance, and shape adaptability. Auxetic materials with these excellent properties show great potential applications in personal protection, medical [...] Read more.

Auxetic materials exhibit a negative Poisson’s ratio under tension or compression, and such counter-intuitive behavior leads to enhanced mechanical properties such as shear resistance, impact resistance, and shape adaptability. Auxetic materials with these excellent properties show great potential applications in personal protection, medical health, sensing equipment, and other fields. However, there are still many limitations in them, from laboratory research to real applications. There have been many reported studies applying auxetic materials or structures to the development of sensing devices in anticipation of improving sensitivity. This review mainly focuses on the use of auxetic materials or auxetic structures in sensors, providing a broad review of auxetic-based sensing devices. The material selection, structure design, preparation method, sensing mechanism, and sensing performance are introduced. In addition, we explore the relationship between the auxetic mechanism and the sensing performance and summarize how the auxetic behavior enhances the sensitivity. Furthermore, potential applications of sensors based on the auxetic mechanism are discussed, and the remaining challenges and future research directions are suggested. This review may help to promote further research and application of auxetic sensing devices. Full article

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14 pages, 2309 KiB

Open AccessArticle

Parameters of Concrete Modified with Micronized Chalcedonite

by Anna Kotwa, Piotr Ramiączek, Paulina Bąk-Patyna and Robert Kowalik

Materials 2023, 16(9), 3602; https://doi.org/10.3390/ma16093602 - 08 May 2023

Cited by 2 | Viewed by 981

Abstract

The PN-EN 197-1:2012 standard allows the use of additives as the main component above 5.0% by mass, as well as as a secondary component in an amount less than 5.0% by mass of cement. Proper selection of additives positively affects the rheological characteristics [...] Read more.

The PN-EN 197-1:2012 standard allows the use of additives as the main component above 5.0% by mass, as well as as a secondary component in an amount less than 5.0% by mass of cement. Proper selection of additives positively affects the rheological characteristics and hardened concrete parameters during longer maturity periods. Additives have already become an integral component of concrete mixes. The aim of the research is to confirm the possibility of using the tested additive in the composition of concrete mixes in an amount of 15% relative to the amount of cement, which would solve the problem of storing and utilizing waste generated during the production of broken chalcedonite aggregates. The planned laboratory tests were carried out for concrete of three classes, C30/37, C35/45, C40/50, according to the PN-EN 206+A1:2016-2 standard, with the addition of chalcedonite dust in a constant amount of 15% relative to cement, and three series without additives as control series. The additive used for concrete mixes was chalcedonite dust with a diameter below 72 μm. It is waste from a broken aggregate mine. The research program included rheological tests of fresh concrete mix, i.e., air content, consistency, bulk density, as well as parameters of hardened concrete mix—compressive strength, absorbability, and capillary uptake. Compressive strength was tested after 7, 14, 28, 56, and 90 days. The laboratory tests aimed to verify whether the addition of 15% chalcedonite dust additive would not worsen the predicted hardened concrete parameters resulting from the designed concrete classes. All three tested series, C30/37, C35/45, and C40/50, with the addition of 15% chalcedonite dust relative to the amount of cement, achieved the assumed strength classes after 28 days of maturation. Concrete mix components were correctly designed. The addition of chalcedonite dust to the concrete mix did not cause a decrease in compressive strength to the extent that the analyzed series did not meet the normative requirements for concrete classes according to the PN-EN 206+A1:2014 standard. The results of absorbability testing indicate water absorption below 5%, while the increase in sample mass in the capillary uptake test gained similar values. Full article

(This article belongs to the Special Issue Durability Studies on the Concrete and Related Composites)

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26 pages, 978 KiB

Open AccessReview

Recent Advances in Synthesis of Graphite from Agricultural Bio-Waste Material: A Review

by Yee Wen Yap, Norsuria Mahmed, Mohd Natashah Norizan, Shayfull Zamree Abd Rahim, Midhat Nabil Ahmad Salimi, Kamrosni Abdul Razak, Ili Salwani Mohamad, Mohd Mustafa Al-Bakri Abdullah and Mohd Yusry Mohamad Yunus

Materials 2023, 16(9), 3601; https://doi.org/10.3390/ma16093601 - 08 May 2023

Cited by 5 | Viewed by 3673

Abstract

Graphitic carbon is a valuable material that can be utilized in many fields, such as electronics, energy storage and wastewater filtration. Due to the high demand for commercial graphite, an alternative raw material with lower costs that is environmentally friendly has been explored. [...] Read more.

Graphitic carbon is a valuable material that can be utilized in many fields, such as electronics, energy storage and wastewater filtration. Due to the high demand for commercial graphite, an alternative raw material with lower costs that is environmentally friendly has been explored. Amongst these, an agricultural bio-waste material has become an option due to its highly bioactive properties, such as bioavailability, antioxidant, antimicrobial, in vitro and anti-inflammatory properties. In addition, biomass wastes usually have high organic carbon content, which has been discovered by many researchers as an alternative carbon material to produce graphite. However, there are several challenges associated with the graphite production process from biomass waste materials, such as impurities, the processing conditions and production costs. Agricultural bio-waste materials typically contain many volatiles and impurities, which can interfere with the synthesis process and reduce the quality of the graphitic carbon produced. Moreover, the processing conditions required for the synthesis of graphitic carbon from agricultural biomass waste materials are quite challenging to optimize. The temperature, pressure, catalyst used and other parameters must be carefully controlled to ensure that the desired product is obtained. Nevertheless, the use of agricultural biomass waste materials as a raw material for graphitic carbon synthesis can reduce the production costs. Improving the overall cost-effectiveness of this approach depends on many factors, including the availability and cost of the feedstock, the processing costs and the market demand for the final product. Therefore, in this review, the importance of biomass waste utilization is discussed. Various methods of synthesizing graphitic carbon are also reviewed. The discussion ranges from the conversion of biomass waste into carbon-rich feedstocks with different recent advances to the method of synthesis of graphitic carbon. The importance of utilizing agricultural biomass waste and the types of potential biomass waste carbon precursors and their pre-treatment methods are also reviewed. Finally, the gaps found in the previous research are proposed as a future research suggestion. Overall, the synthesis of graphite from agricultural bio-waste materials is a promising area of research, but more work is needed to address the challenges associated with this process and to demonstrate its viability at scale. Full article

(This article belongs to the Special Issue Recycling and Processing of Waste Materials)

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20 pages, 4226 KiB

Open AccessArticle

Determination of the Effect of Wastewater on the Biological Activity of Mixtures of Fluoxetine and Its Metabolite Norfluoxetine with Nalidixic and Caffeic Acids with Use of E. coli Microbial Bioindicator Strains

by Marzena Matejczyk, Piotr Ofman, Józefa Wiater, Renata Świsłocka, Paweł Kondzior and Włodzimierz Lewandowski

Materials 2023, 16(9), 3600; https://doi.org/10.3390/ma16093600 - 08 May 2023

Cited by 1 | Viewed by 1165

Abstract

In the present work, the conducted research concerned the determination of the toxicity and oxidative stress generation of the antidepressant fluoxetine (FLU), its metabolite nor-fluoxetine (Nor-FLU), the antibiotic nalidixic acid (NA), caffeic acid (CA) and their mixtures in three different environments: microbial medium [...] Read more.

In the present work, the conducted research concerned the determination of the toxicity and oxidative stress generation of the antidepressant fluoxetine (FLU), its metabolite nor-fluoxetine (Nor-FLU), the antibiotic nalidixic acid (NA), caffeic acid (CA) and their mixtures in three different environments: microbial medium (MM), raw wastewaters (RW) and treated wastewaters (TW). We evaluated the following parameters: E. coli cell viability, toxicity and protein damage, sodA promoter induction and ROS generation. It was found that FLU, Nor-FLU, NA, CA and their mixtures are toxic and they have the potency to generate oxidative stress in E. coli strains. We also detected that the wastewater, in comparison to the microbial medium, had an influence on the toxic activity and oxidative stress synthesis of the tested chemicals and their mixtures. Regardless of the environment under study, the strongest toxic activity and oxidative stress generation were detected after bacterial incubation with NA at a concentration of 1 mg/dm³ and the mixture of FLU (1 mg/dm³) with Nor-FLU (0.1 mg/dm³) and with NA (0.1 mg/dm³). The ROS synthesis and sodA promoter induction suggest that, in the case of the examined compounds and their mixtures, oxidative stress is the mechanism of toxicity. The analysis of the types of interactions among the substances constituting the mixtures in the wastewater revealed synergism, potentiation and antagonism. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Chemistry)

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21 pages, 19080 KiB

Open AccessArticle

Effect of Mg/Si Ratio on the Bendability and Anisotropic Bend Behavior of Extruded 6000-Series Al Alloy

by Qi Zhang, Xiaochang Xu and Yu Wang

Materials 2023, 16(9), 3599; https://doi.org/10.3390/ma16093599 - 08 May 2023

Viewed by 992

Abstract

Extruded Al-Mg-Si profiles applied in the automotive industry are required to achieve an appropriate combination of strength and bendability. In order to investigate the effect of Mg/Si ratio on the bendability and anisotropic bending behavior, AA6005 and AA6061C were extruded to 2 mm [...] Read more.

Extruded Al-Mg-Si profiles applied in the automotive industry are required to achieve an appropriate combination of strength and bendability. In order to investigate the effect of Mg/Si ratio on the bendability and anisotropic bending behavior, AA6005 and AA6061C were extruded to 2 mm thick plates. More Goss texture and anisotropic particle clusters exist in AA6005 alloys with a low Mg/Si ratio, which leads to a high tendency of surface roughing and cracking and to strong anisotropy in their bendability. However, more low-angle grain boundaries, cubic texture and comparatively random distribution of particles exists in AA6061C alloys with a high Mg/Si ratio, which blunts the surface roughing and crack process. The surface undulation is the outcome of the strain-intense localization of several layers of grains in the vicinity of the outer elongated surface. The strain localization and surface undulation lead to shear band initiation near the valleys. Several cooperating micro-mechanisms in AA6005, including grain clusters with Goss and Cubic orientation, heterogeneously nucleated particles and grain boundary spatial arrangements, lead to the grain boundary decohesion along a shear direction. AA6005 shows for predominately intergranular fractures in nature, with some areas exhibiting grain boundary decohesion during bending in the TD. However, AA6061C shows a predominately transgranular in nature, with some areas exhibiting intergranular fracture, which is affected by shear band development. Full article

(This article belongs to the Section Mechanics of Materials)

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16 pages, 9623 KiB

Open AccessEditor’s ChoiceArticle

Synergistic Effects of 2-Butyne-1,4-Diol and Chloride Ions on the Microstructure and Residual Stress of Electrodeposited Nickel

by Ming Sun, Chao Zhang, Ruhan Ya, Hongyu He, Zhipeng Li and Wenhuai Tian

Materials 2023, 16(9), 3598; https://doi.org/10.3390/ma16093598 - 08 May 2023

Viewed by 1122

Abstract

To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And [...] Read more.

To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And their surface morphologies, microstructure, and residual stress were tested using SEM, XRD, EBSD, TEM, and AFM. While the nickel layers composed of pyramid morphology were prepared from additive-free baths, the surface flattened gradually as the BD concentration of the baths was increased, and the acicular grains in the deposits were replaced with <100> oriented columnar grains or <111> oriented nanograins; additionally, the residual tensile stress of the deposits increased. The addition of chloride ions to the baths containing BD significantly increased the residual stress in the nickel layers, although it only slightly promoted surface flattening and columnar grain coarsening. The effects of BD and chloride ions on the growth mode and residual stress of nickel deposits were explained via analysis of surface morphologies and microstructure. And the results indicate that the reduction of chloride ion concentration is a feasible way to reduce the residual stress of the nickel deposits when BD is included in the baths. Full article

(This article belongs to the Special Issue Advances in Coatings Prepared by Deposition: Microstructure, Properties and Applications)

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14 pages, 10272 KiB

Open AccessArticle

Removal of Methylene Blue from Aqueous Solutions by Surface Modified Talc

by Shuyang Chen, Mei Zhang, Hanjie Chen and Ying Fang

Materials 2023, 16(9), 3597; https://doi.org/10.3390/ma16093597 - 08 May 2023

Cited by 1 | Viewed by 1050

Abstract

In this study, raw talc powder surface modification was conducted, and the powder was modified in two different methods using acid washing and ball milling. Modified talc was characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). [...] Read more.

In this study, raw talc powder surface modification was conducted, and the powder was modified in two different methods using acid washing and ball milling. Modified talc was characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). In order to investigate the adsorption capacity of modified talc on dyes, adsorption experiments were carried out with methylene blue (MB) in aqueous solutions as the target contaminant. The findings of the characterization revealed that both modifications increased the adsorption capacity of talc, which was attributed to changes in specific surface area and active groups. The influence of process parameters such as contact time, pH, dye concentration, and adsorbent dosage on the adsorption performance was systematically investigated. Modified talc was able to adsorb MB rapidly, reaching equilibrium within 60 min. Additionally, the adsorption performance was improved as the pH of the dye solution increased. The isotherms for MB adsorption by modified talc fitted well with the Langmuir model. The pseudo-second-order model in the adsorption kinetic model properly described the adsorption behavior. The results show that the modified talc can be used as an inexpensive and abundant candidate material for the adsorption of dyes in industrial wastewater. Full article

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23 pages, 11793 KiB

Open AccessEditor’s ChoiceReview

Plasmonic Functionality of Optical Fiber Tips: Mechanisms, Fabrications, and Applications

by Bobo Du, Yunfan Xu, Lei Zhang and Yanpeng Zhang

Materials 2023, 16(9), 3596; https://doi.org/10.3390/ma16093596 - 08 May 2023

Cited by 1 | Viewed by 1497

Abstract

Optical fiber tips with the flat end-facets functionalized take the special advantages of easy fabrication, compactness, and ready-integration among the community of optical fiber devices. Combined with plasmonic structures, the fiber tips draw a significant growth of interest addressing diverse functions. This review [...] Read more.

Optical fiber tips with the flat end-facets functionalized take the special advantages of easy fabrication, compactness, and ready-integration among the community of optical fiber devices. Combined with plasmonic structures, the fiber tips draw a significant growth of interest addressing diverse functions. This review aims to present and summarize the plasmonic functionality of optical fiber tips with the current state of the art. Firstly, the mechanisms of plasmonic phenomena are introduced in order to illustrate the tip-compatible plasmonic nanostructures. Then, the strategies of plasmonic functionalities on fiber tips are analyzed and compared. Moreover, the classical applications of plasmonic fiber tips are reviewed. Finally, the challenges and prospects for future opportunities are discussed. Full article

(This article belongs to the Special Issue Advances in Multimaterial Fibers and Devices)

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14 pages, 4022 KiB

Open AccessArticle

The Effect of CH on Improving the Carbonation Resistance of OPC-CSA Binary Blends

by Shunqin Yang, Guoxin Li and Ge Zhang

Materials 2023, 16(9), 3595; https://doi.org/10.3390/ma16093595 - 08 May 2023

Cited by 1 | Viewed by 900

Abstract

Due to the large amount of CO₂ generated during steelmaking, to resume production as soon as possible, a fast repair material with good carbonation resistance is needed to repair the factory building. First, the performance of an ordinary Portland cement (OPC)-calcium sulfoaluminate [...] Read more.

Due to the large amount of CO₂ generated during steelmaking, to resume production as soon as possible, a fast repair material with good carbonation resistance is needed to repair the factory building. First, the performance of an ordinary Portland cement (OPC)-calcium sulfoaluminate cement (CSA) system under an accelerated carbonization environment was studied. Next, the OPC-CSA system with a CSA content of 15 wt% was selected to be modified by adding calcium hydroxide (CH). The findings showed that the addition of 15 wt% CSA to the OPC-CSA system resulted in the highest mechanical properties. Specifically, the flexural strength and compressive strength after 84 d of carbonization were 18% and 15% higher, respectively, compared to those of OPC alone. The degradation of the mechanical properties of the OPC-CSA system due to carbonation was improved by adding CH. The flexural strength (3.0 wt% CH) and the compressive strength (4.5 wt% CH) of the OPC-CSA-CH system after 84 d of carbonization were 13% and 5% higher, respectively, than those of the OPC-CSA system. The addition of CH increased the alkalinity of the OPC-CSA system and enhanced the stability of Aft, resulting in better carbonation resistance in the OPC-CSA-CH system. Full article

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14 pages, 2114 KiB

Open AccessArticle

Experimental Study of Fiber Pull-Outs in a Polymer Mortar Matrix

by Lihua Wang, Tongshuai Li, Qinghua Shu, Shifu Sun, Chunfeng Li and Chunquan Dai

Materials 2023, 16(9), 3594; https://doi.org/10.3390/ma16093594 - 08 May 2023

Viewed by 1045

Abstract

In order to study the influence of vinyl acetate–ethylene copolymerization emulsions on the bonding performance of fiber and mortar, mortar materials with different polymer contents were prepared. The optimal mix ratio of the matrix was obtained using a pull-out test with a 0° [...] Read more.

In order to study the influence of vinyl acetate–ethylene copolymerization emulsions on the bonding performance of fiber and mortar, mortar materials with different polymer contents were prepared. The optimal mix ratio of the matrix was obtained using a pull-out test with a 0° inclination angle. On this basis, polypropylene fibers and alkali-resistant glass fibers were set at different burial depths (6 mm, 12 mm, and 18 mm) and different burial angles (0°, 30°, 45°, and 60°). The load–displacement curves of two types of fibers pulled out from the polymer mortar were obtained. The test results show that polymer contents of 3% and 5% increase the peak pull-out loads of glass fibers and polypropylene fibers by 16.28% and 30.72% and 7.41% and 27.11%, respectively. When the polymer content is 7%, the peak pull-out load decreases by 1.31% and 24.26%, especially for polypropylene fiber, which significantly weakens the bonding performance between the matrix and the fiber. The pull-out load of glass fibers and polypropylene fibers increases with the increase in the buried depth, and both show tensile failure at 18 mm. As the embedding angle increases, the pull-out load of polypropylene fibers decreases continuously, while the glass fiber shows a higher pull-out load at 30°. Full article

(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites)

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16 pages, 5608 KiB

Open AccessArticle

Clarithromycin-Loaded Submicron-Sized Carriers: Pharmacokinetics and Pharmacodynamic Evaluation

by Reetika Rawat, Raghuraj Singh Chouhan, Veera Sadhu and Manu Sharma

Materials 2023, 16(9), 3593; https://doi.org/10.3390/ma16093593 - 08 May 2023

Viewed by 1288

Abstract

The current study aims to improve clarithromycin bioavailability and effectiveness in complicated intra-abdominal infection management. Therefore, clarithromycin-loaded submicron dual lipid carriers (CLA-DLCs) were developed via hot high shear homogenization technique and evaluated for colloidal parameters, release behavior, stability study, and in-vitro antibiofilm activity. [...] Read more.

The current study aims to improve clarithromycin bioavailability and effectiveness in complicated intra-abdominal infection management. Therefore, clarithromycin-loaded submicron dual lipid carriers (CLA-DLCs) were developed via hot high shear homogenization technique and evaluated for colloidal parameters, release behavior, stability study, and in-vitro antibiofilm activity. Bioavailability and therapeutic efficacy of optimized formulation on hampering cytokines storm induction was determined in E. coli-induced peritonitis. The developed CLA-DLCs (particle size 326.19 ± 24.14 nm, zeta potential −31.34 ± 2.81 mV, and entrapment efficiency 85.78 ± 4.01%) exhibited smooth spherical shapes and sustained in vitro release profiles. Long-term stability study of optimized CLA-DLCs ensured maintenance of colloidal parameters for 1 year at room temperature. In vitro antimicrobial studies revealed 3.43-fold higher anti-biofilm activity of CLA-DLCs compared with clarithromycin. In addition, the relative bioavailability of CLA-DLCs was enhanced 5.89-fold compared to pure drug in rats. The remarkable decrease in microbial burden in blood as well as tissues, along with oxidative stress markers (lipid peroxidation, myeloperoxidase activity, and carbonylated protein level) and immunological markers (total leukocyte count, neutrophil migration, NO, TNF-, and IL-6) on treatment with CLA-DLCs enhanced the survival in a rat model of peritonitis compared with the pure drug and untreated groups. In conclusion, CLA-DLCs hold promising potential in management of intra-abdominal infections and prevention of associated complications. Full article

(This article belongs to the Special Issue Nanomaterials-Based Biosensor Platforms for Environmental and Biomedical Applications)

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12 pages, 4731 KiB

Open AccessArticle

Ex Situ Study on the Co-Preparation of Pitch and Carbon Black from Petroleum Residue to Improve the Cost-Efficiency of the Pitch Synthesis Plant

by Ji-Hong Kim

Materials 2023, 16(9), 3592; https://doi.org/10.3390/ma16093592 - 08 May 2023

Cited by 1 | Viewed by 1061

Abstract

This study aims to improve the economic efficiency of the pitch synthesis reaction on the pilot plant by optimizing the pitch synthesis reaction and utilization of the byproduct. The pitch was synthesized using a 150 L pilot plant with pyrolyzed fuel oil as [...] Read more.

This study aims to improve the economic efficiency of the pitch synthesis reaction on the pilot plant by optimizing the pitch synthesis reaction and utilization of the byproduct. The pitch was synthesized using a 150 L pilot plant with pyrolyzed fuel oil as a precursor. The pitch synthesis reaction is carried out through volatilization and polycondensation, which occur at 300 and 400 °C. Volatilization is terminated during heating; thus, additional soaking time is meaningless and reduces the process efficiency. Soaking time is a major variable when the synthesis temperature exceeds 400 °C. The byproduct is generated through volatilization; thus, its chemical characteristics are only influenced by the reaction temperature. The byproduct consists of various polycyclic aromatic hydrocarbons. The average molecular weight and yield of the byproduct increase with the reaction temperature. Carbon black was synthesized using chemical vapor deposition from the byproduct. The particle size of carbon black was controlled by the used precursor (byproduct), and the electrical conductivity of prepared carbon black has a maximum of 58.0 S/cm. Therefore, carbon black, which is synthesized from the byproduct of pitch synthesis, is expected to be used as a precursor for conductive material used in lithium-ion batteries or supercapacitors. Full article

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14 pages, 5231 KiB

Open AccessArticle

The Influence of the Strain Rate and Prestatic Stress on the Dynamic Mechanical Properties of Sandstone—A Case Study from China

by Jun Wang, Zhiwei Ren, Shang Yang, Jianguo Ning, Shuai Zhang and Yongtian Bian

Materials 2023, 16(9), 3591; https://doi.org/10.3390/ma16093591 - 08 May 2023

Cited by 2 | Viewed by 1256

Abstract

A series of conventional dynamic uniaxial compressive (CDUC) tests and coupled static dynamic loading (CSDL) tests were performed using a split Hopkinson compression bar (SHPB) system to explore the variable dynamic mechanical behavior and fracture characteristics of medium siltstone at a microscopic scale [...] Read more.

A series of conventional dynamic uniaxial compressive (CDUC) tests and coupled static dynamic loading (CSDL) tests were performed using a split Hopkinson compression bar (SHPB) system to explore the variable dynamic mechanical behavior and fracture characteristics of medium siltstone at a microscopic scale in the laboratory. In the CDUC tests, the dynamic uniaxial strength of the medium sandstone is rate-dependent in the range of 17.5 to 96.8 s⁻¹, while the dynamic elastic modulus is not dependent on the strain rate. Then, this paper proposes a generalized model to characterize the rate-dependent strength from 17.5 to 96.8 s⁻¹. In the CSDL tests, with increasing initial prestatic stress, the dynamic elastic modulus and dynamic strength increase nonlinearly at first and then decrease. The results show that two classical morphological types (i.e., Type I and Type II) are observed in the dynamic stress–strain response from the CDUC and CSDL tests. By scanning electron microscopy (SEM), microscopic differences in the post-loading microcrack characteristics in the behavior of Type I and Type II are identified. In Class I behavior, intergranular fracture (IF) usually initiates at or near the grains, with most cracks deflected along the grain boundaries, resulting in a sharp angular edge, and then coalesces to the main fracture surface that splits the specimen along the direction of stress wave propagation. In contrast, Class II behavior results from the combined IF and transgranular fracture (TF). Full article

(This article belongs to the Special Issue Microstructure, Characterization and Mechanical Properties of Coal and Coal-Like Materials (Volume II))

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18 pages, 6740 KiB

Open AccessArticle

Effects of Waste Glass Powder on Rheological and Mechanical Properties of Calcium Carbide Residue Alkali-Activated Composite Cementitious Materials System

by Youzhi Chen, Xiuqi Wu, Weisong Yin, Shichang Tang and Ge Yan

Materials 2023, 16(9), 3590; https://doi.org/10.3390/ma16093590 - 08 May 2023

Cited by 1 | Viewed by 1479

Abstract

As a municipal solid waste, waste glass undergoes pozzolanic activity when ground to a certain fineness. In this paper, calcium carbide residue (CCR) and Na₂CO₃ were used as composite alkali activators for a glass powder-based composite cementitious system. A total [...] Read more.

As a municipal solid waste, waste glass undergoes pozzolanic activity when ground to a certain fineness. In this paper, calcium carbide residue (CCR) and Na₂CO₃ were used as composite alkali activators for a glass powder-based composite cementitious system. A total of 60% fly ash (FA) and 40% ground granulated blast furnace slag (GGBS) were used as the reference group of the composite cementitious material system, and the effects of 5%, 10%, 15%, and 20% glass powder (GP) replacing FA on the rheological behavior, mechanical properties, and microstructure of alkali-activated composite cementitious systems were investigated. The results showed that with the increase in GP replacing FA, the fluidity of the alkali-activated materials gradually decreased, the shear stress and the equivalent plastic viscosity both showed an increasing trend, and the paste gradually changed from shear thinning to shear thickening. Compared with the reference sample, the fluidity of the alkali-activated material paste with a 20% GP replacement of FA was reduced by 15.3%, the yield shear stress was increased by 49.6%, and the equivalent plastic viscosity was elevated by 32.1%. For the 28d alkali-activated material pastes, the compressive strength and flexural strength were increased by 13% and 20.3%, respectively. The microstructure analysis showed the substitution of FA by GP promoted the alkali-activated reaction to a certain extent, and more C-A-S-H gel was formed. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials)

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10 pages, 5354 KiB

Open AccessArticle

Microstructural Changes and Mechanical Properties of Precipitation-Strengthened Medium-Entropy Fe_71.25(CoCrMnNi)_23.75Cu₃Al₂ Maraging Alloy

by Unhae Lee and Jae Wung Bae

Materials 2023, 16(9), 3589; https://doi.org/10.3390/ma16093589 - 07 May 2023

Viewed by 1162

Abstract

Metal alloys with enhanced mechanical properties are in considerable demand in various industries. Thus, this study focused on the development of nanosized precipitates in Fe_71.25(CoCrMnNi)_23.75Cu₃Al₂ maraging medium-entropy alloy (MEA). The Fe-based alloying design in the MEA [...] Read more.

Metal alloys with enhanced mechanical properties are in considerable demand in various industries. Thus, this study focused on the development of nanosized precipitates in Fe_71.25(CoCrMnNi)_23.75Cu₃Al₂ maraging medium-entropy alloy (MEA). The Fe-based alloying design in the MEA samples initially formed a body-centered cubic (BCC) lath martensite structure. After a subsequent annealing process at 450 °C for varying durations (1, 3, 5, and 7 h), nanosized precipitates (B2 intermetallic) enriched with Cu and with a diameter of approximately 5 nm formed, significantly increasing the hardness of the alloy. The highest Vickers microhardness of 597 HV, along with compressive yield strength and ultimate compressive strength of 2079 MPa and 2843 MPa, respectively, was achieved for the Aged_7h sample. Therefore, the BCC lath martensite structure with B2 intermetallics leads to remarkable mechanical properties. Full article

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

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18 pages, 6570 KiB

Open AccessEditor’s ChoiceArticle

Fracture Response of X80 Pipe Girth Welds under Combined Internal Pressure and Bending Moment

by Li Zhu, Naixian Li, Bin Jia and Yu Zhang

Materials 2023, 16(9), 3588; https://doi.org/10.3390/ma16093588 - 07 May 2023

Cited by 1 | Viewed by 1428

Abstract

In order to determine the effect of defect size on the pipeline fracture performance of girth welds in oil and gas pipelines, ABAQUS was used to simulate the fracture responses of X80 pipelines with girth weld defects under internal pressure and bending moment [...] Read more.

In order to determine the effect of defect size on the pipeline fracture performance of girth welds in oil and gas pipelines, ABAQUS was used to simulate the fracture responses of X80 pipelines with girth weld defects under internal pressure and bending moment conditions based on damage mechanics. In particular, the length and depth of defects were parametrically studied; the defect depth range was 20–80% of the wall thickness, and the circumferential length range of the defects was 5–20% of the pipeline circumference. The results show that, under the combined action of internal pressure and bending moment, the defect depth was more associated with adverse effects than the circumferential length of the defect. The failure load did not linearly decrease as the size of the defect increased, but when the depth of the defect reached a certain value, the failure load suddenly decreased. Full article

(This article belongs to the Special Issue Mechanics Behavior, Fatigue Damage, and Microstructure Evolution of Metallic Material)

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13 pages, 3264 KiB

Open AccessArticle

Design and Characteristic Analysis of an Axial Flux High-Temperature Superconducting Motor for Aircraft Propulsion

by Jun-Yeop Lee, Gi-Dong Nam, In-Keun Yu and Minwon Park

Materials 2023, 16(9), 3587; https://doi.org/10.3390/ma16093587 - 07 May 2023

Cited by 2 | Viewed by 1915

Abstract

In line with global environmental regulations, the demand for eco-friendly and highly efficient aircraft propulsion systems is increasing. The combination of axial flux motors and superconductors could be a key technology used to address these needs. In this paper, an axial flux high [...] Read more.

In line with global environmental regulations, the demand for eco-friendly and highly efficient aircraft propulsion systems is increasing. The combination of axial flux motors and superconductors could be a key technology used to address these needs. In this paper, an axial flux high temperature superconducting (HTS) motor for aircraft propulsion was designed and its characteristics were analyzed. A 2G HTS wire with high magnetic flux characteristic was used for the field winding of the 120 kW axial flux HTS motor, and the rotational speed and rated voltage of the motor were 2000 rpm and 220 V, respectively. The axial flux HTS motor implements a revolving armature type for solid cooling of the HTS field coil. The electromagnetic and thermal features of the motor were analyzed and designed utilizing a 3D finite element method program. The HTS coil was maintained at the target temperature by effectively designing the current lead and cooling system to minimize heat loss. These results can be effectively used in the design of propulsion systems for large commercial aircraft in the future as well as for the design of small aircraft with less than 4 seats. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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14 pages, 3396 KiB

Open AccessArticle

Miconazole Nitrate Microparticles in Lidocaine Loaded Films as a Treatment for Oropharyngeal Candidiasis

by Guillermo Tejada, Natalia L. Calvo, Mauro Morri, Maximiliano Sortino, Celina Lamas, Vera A. Álvarez and Darío Leonardi

Materials 2023, 16(9), 3586; https://doi.org/10.3390/ma16093586 - 07 May 2023

Cited by 2 | Viewed by 1717

Abstract

Oral candidiasis is an opportunistic infection that affects mainly individuals with weakened immune system. Devices used in the oral area to treat this condition include buccal films, which present advantages over both oral tablets and gels. Since candidiasis causes pain, burning, and itching, [...] Read more.

Oral candidiasis is an opportunistic infection that affects mainly individuals with weakened immune system. Devices used in the oral area to treat this condition include buccal films, which present advantages over both oral tablets and gels. Since candidiasis causes pain, burning, and itching, the purpose of this work was to develop buccal films loaded with both lidocaine (anesthetic) and miconazole nitrate (MN, antifungal) to treat this pathology topically. MN was loaded in microparticles based on different natural polymers, and then, these microparticles were loaded in hydroxypropyl methylcellulose-gelatin-based films containing lidocaine. All developed films showed adequate adhesiveness and thickness. DSC and XRD tests suggested that the drugs were in an amorphous state in the therapeutic systems. Microparticles based on chitosan-alginate showed the highest MN encapsulation. Among the films, those containing the mentioned microparticles presented the highest tensile strength and the lowest elongation at break, possibly due to the strong interactions between both polymers. These films allowed a fast release of lidocaine and a controlled release of MN. Due to the latter, these systems showed antifungal activity for 24 h. Therefore, the treatment of oropharyngeal candidiasis with these films could reduce the number of daily applications with respect to conventional treatments. Full article

(This article belongs to the Special Issue Functionalized Nanomaterials and Structures for Biomedical Applications)

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12 pages, 3461 KiB

Open AccessArticle

Corrosion Resistance of Al_0.5CoCrFeNiCu_xAg_y (x = 0.25, 0.5; y = 0, 0.1) High-Entropy Alloys in 0.5M H₂SO₄ Solution

by Olga Samoilova, Svetlana Pratskova, Nataliya Shaburova, Ahmad Ostovari Moghaddam and Evgeny Trofimov

Materials 2023, 16(9), 3585; https://doi.org/10.3390/ma16093585 - 07 May 2023

Cited by 4 | Viewed by 1182

Abstract

The electrochemical behavior of the as-cast Al_0.5CoCrFeNiCu_xAg_y (x = 0.25, 0.5; y = 0, 0.1) high-entropy alloys (HEAs) in a 0.5M H₂SO₄ solution was studied. Polarization measurements were carried out in a standard three-electrode [...] Read more.

The electrochemical behavior of the as-cast Al_0.5CoCrFeNiCu_xAg_y (x = 0.25, 0.5; y = 0, 0.1) high-entropy alloys (HEAs) in a 0.5M H₂SO₄ solution was studied. Polarization measurements were carried out in a standard three-electrode electrochemical cell at room temperature using a platinum counter electrode and a saturated silver chloride reference electrode. For Al_0.5CoCrFeNiCu_0.5 and Al_0.5CoCrFeNiCu_0.5Ag_0.1, copper segregation along the grain boundaries was observed, which highly dissolved in the sulfuric acid solution and resulted in low corrosion resistance of the samples. Introducing Ag into Al_0.5CoCrFeNiCu_0.25 HEA led to the precipitation of a copper–silver eutectic structure, in which the copper regions were selectively dissolved in the sulfuric acid solution. Al_0.5CoCrFeNiCu_0.25 exhibited the best corrosion resistance with the corrosion current density of I_corr = 3.52 ± 0.02 μA/cm², significantly superior to that of the Al_0.5CoCrFeNi sample without copper and silver (I_corr = 6.05 ± 0.05 μA/cm²). Finally, the results indicated that suppressing elemental segregation by annealing or tailoring chemical composition is essential to improve the corrosion resistance of Al_0.5CoCrFeNiCu_xAg_y HEAs. Full article

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14 pages, 4200 KiB

Open AccessArticle

Investigating the Effect of Reflectance Tuning on Photocatalytic Dye Degradation with Biotemplated ZnO Photonic Nanoarchitectures Based on Morpho Butterfly Wings

by Gábor Piszter, Gergely Nagy, Krisztián Kertész, Zsófia Baji, Krisztina Kovács, Zsolt Bálint, Zsolt Endre Horváth, József Sándor Pap and László Péter Biró

Materials 2023, 16(9), 3584; https://doi.org/10.3390/ma16093584 - 07 May 2023

Cited by 1 | Viewed by 1433

Abstract

Photonic nanoarchitectures of butterfly wings can serve as biotemplates to prepare semiconductor thin films of ZnO by atomic layer deposition. The resulting biotemplated ZnO nanoarchitecture preserves the structural and optical properties of the natural system, while it will also have the features of [...] Read more.

Photonic nanoarchitectures of butterfly wings can serve as biotemplates to prepare semiconductor thin films of ZnO by atomic layer deposition. The resulting biotemplated ZnO nanoarchitecture preserves the structural and optical properties of the natural system, while it will also have the features of the functional material. The ZnO-coated wings can be used directly in heterogeneous photocatalysis to decompose pollutants dissolved in water upon visible light illumination. We used the photonic nanoarchitectures of different Morpho butterflies with different structural colors as biotemplates and examined the dependence of decomposition rates of methyl orange and rhodamine B dyes on the structural color of the biotemplates and the thickness of the ZnO coating. Using methyl orange, we measured a ten-fold increase in photodegradation rate when the 20 nm ZnO-coated wings were compared to similarly coated glass substrates. Using rhodamine B, a saturating relationship was found between the degradation rate and the thickness of the deposited ZnO on butterfly wings. We concluded that the enhancement of the catalytic efficiency can be attributed to the slow light effect due to a spectral overlap between the ZnO-coated Morpho butterfly wings reflectance with the absorption band of dyes, thus the photocatalytic performance could be changed by the tuning of the structural color of the butterfly biotemplates. The photodegradation mechanism of the dyes was investigated by liquid chromatography–mass spectroscopy. Full article

(This article belongs to the Special Issue Application of Photocatalytic Technology in Environmental Sustainability)

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30 pages, 9216 KiB

Open AccessArticle

Stochastic Vibrations of a System of Plates Immersed in Fluid Using a Coupled Boundary Element, Finite Element, and Finite Difference Methods Approach

by Michał Guminiak, Marcin Kamiński, Agnieszka Lenartowicz and Maciej Przychodzki

Materials 2023, 16(9), 3583; https://doi.org/10.3390/ma16093583 - 07 May 2023

Cited by 1 | Viewed by 1185

Abstract

The main objective of this work is to investigate the natural vibrations of a system of two thin (Kirchhoff–Love) plates surrounded by liquid in terms of the coupled Stochastic Boundary Element Method (SBEM), Stochastic Finite Element Method (SFEM), and Stochastic Finite Difference Method [...] Read more.

The main objective of this work is to investigate the natural vibrations of a system of two thin (Kirchhoff–Love) plates surrounded by liquid in terms of the coupled Stochastic Boundary Element Method (SBEM), Stochastic Finite Element Method (SFEM), and Stochastic Finite Difference Method (SFDM) implemented using three different probabilistic approaches. The BEM, FEM, and FDM were used equally to describe plate deformation, and the BEM was applied to describe the dynamic interaction of water on a plate surface. The plate’s inertial forces were expressed using a diagonal or consistent mass matrix. The inertial forces of water were described using the mass matrix, which was fully populated and derived using the theory of double-layer potential. The main aspect of this work is the simultaneous application of the BEM, FEM, and FDM to describe and model the problem of natural vibrations in a coupled problem in solid–liquid mechanics. The second very important novelty of this work is the application of the Bhattacharyya relative entropy apparatus to test the safety of such a system in terms of potential resonance. The presented concept is part of a solution to engineering problems in the field of structure and fluid dynamics and can also be successfully applied to the analysis of the dynamics of the control surfaces of ships or aircraft. Full article

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39 pages, 6396 KiB

Open AccessReview

A Review of Oxygen Carrier Materials and Related Thermochemical Redox Processes for Concentrating Solar Thermal Applications

by Stéphane Abanades

Materials 2023, 16(9), 3582; https://doi.org/10.3390/ma16093582 - 07 May 2023

Cited by 2 | Viewed by 2326

Abstract

Redox materials have been investigated for various thermochemical processing applications including solar fuel production (hydrogen, syngas), ammonia synthesis, thermochemical energy storage, and air separation/oxygen pumping, while involving concentrated solar energy as the high-temperature process heat source for solid–gas reactions. Accordingly, these materials can [...] Read more.

Redox materials have been investigated for various thermochemical processing applications including solar fuel production (hydrogen, syngas), ammonia synthesis, thermochemical energy storage, and air separation/oxygen pumping, while involving concentrated solar energy as the high-temperature process heat source for solid–gas reactions. Accordingly, these materials can be processed in two-step redox cycles for thermochemical fuel production from H₂O and CO₂ splitting. In such cycles, the metal oxide is first thermally reduced when heated under concentrated solar energy. Then, the reduced material is re-oxidized with either H₂O or CO₂ to produce H₂ or CO. The mixture forms syngas that can be used for the synthesis of various hydrocarbon fuels. An alternative process involves redox systems of metal oxides/nitrides for ammonia synthesis from N₂ and H₂O based on chemical looping cycles. A metal nitride reacts with steam to form ammonia and the corresponding metal oxide. The latter is then recycled in a nitridation reaction with N₂ and a reducer. In another process, redox systems can be processed in reversible endothermal/exothermal reactions for solar thermochemical energy storage at high temperature. The reduction corresponds to the heat charge while the reverse oxidation with air leads to the heat discharge for supplying process heat to a downstream process. Similar reversible redox reactions can finally be used for oxygen separation from air, which results in separate flows of O₂ and N₂ that can be both valorized, or thermochemical oxygen pumping to absorb residual oxygen. This review deals with the different redox materials involving stoichiometric or non-stoichiometric materials applied to solar fuel production (H₂, syngas, ammonia), thermochemical energy storage, and thermochemical air separation or gas purification. The most relevant chemical looping reactions and the best performing materials acting as the oxygen carriers are identified and described, as well as the chemical reactors suitable for solar energy absorption, conversion, and storage. Full article

(This article belongs to the Section Energy Materials)

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22 pages, 10465 KiB

Open AccessArticle

Effect of Sodium Gluconate on Properties and Microstructure of Ultra-High-Performance Concrete (UHPC)

by Yonghua Wu, Yibing Yuan, Mengdie Niu and Yufeng Kuang

Materials 2023, 16(9), 3581; https://doi.org/10.3390/ma16093581 - 07 May 2023

Cited by 1 | Viewed by 1366

Abstract

The properties of concrete can be significantly affected by sodium gluconate (SG) at very small dosages. In this paper, the effects of SG on the fluidity, setting time, heat of hydration, and strength of ultra-high-performance concrete (UHPC) were studied. The results show that [...] Read more.

The properties of concrete can be significantly affected by sodium gluconate (SG) at very small dosages. In this paper, the effects of SG on the fluidity, setting time, heat of hydration, and strength of ultra-high-performance concrete (UHPC) were studied. The results show that (1) in the plastic stage, SG inhibited the formation of early ettringite (AFt) and delayed the hydration of tricalcium silicate (C₃S) and dicalcium silicate (C₂S). SG increased the initial fluidity of UHPC without decreasing within 1 h. When the SG dosage was ≥0.06%, the slumps at 30 min and 60 min increased slightly. (2) In the setting hardening stage, the addition of SG inhibited the formation of calcium hydroxide (CH), which significantly extended the setting time of UHPC. When the dosage of SG was 0.15%, the initial and final setting times were 5.0 times and 4.5 times that of the blank group, respectively. SG had no obvious effect on the hydration rate of cement in the accelerated period, but the peak hydration temperature of UHPC was increased when the SG dosage was 0.03~0.12%. (3) In the strength development stage, the 1 d and 3 d strength of UHPC decreased significantly with the increase in the SG dosage. However, SG could promote the formation of AFt at the pores and aggregate interface in the later stage, reduce the porosity of cementite, and improve the compressive strength of UHPC in 28 d, 60 d, and 90 d. When the SG dosage was 0.12%, the 90d strength increased by 13%. Full article

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

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12 pages, 1665 KiB

Open AccessArticle

Three-Dimensional Printed Resin: Impact of Different Cleaning Protocols on Degree of Conversion and Tensile Bond Strength to a Composite Resin Using Various Adhesive Systems

by Valerie Lankes, Marcel Reymus, Felicitas Mayinger, Andrea Coldea, Anja Liebermann, Moritz Hoffmann and Bogna Stawarczyk

Materials 2023, 16(9), 3580; https://doi.org/10.3390/ma16093580 - 07 May 2023

Cited by 1 | Viewed by 1361

Abstract

The present investigation tested the effect of cleaning methods and adhesives on the tensile bond strength (TBS) of a resin-based composite luted to a temporary 3D printed resin. Substrates (n= 360) were printed using a Rapidshape D20II and cleaned with a [...] Read more.

The present investigation tested the effect of cleaning methods and adhesives on the tensile bond strength (TBS) of a resin-based composite luted to a temporary 3D printed resin. Substrates (n= 360) were printed using a Rapidshape D20II and cleaned with a butyldiglycol-based solution, isopropanol, or by centrifugation. Specimens were air-abraded with Al₂O₃ (mean particle size 50 µm) at 0.1 MPa followed by pretreatment (n = 30/subgroup) with: (1) Clearfil Ceramic Primer (CCP); (2) Clearfil Universal Bond (CUB); (3) Scotchbond Universal Plus (SUP) or 4. Visio.link (VL) and luted to PanaviaV5. TBS (n = 15/subgroup) was measured initially (24 h at 37 °C water) or after thermal cycling (10,000×, 5/55 °C). The degree of conversion (DC) for each cleaning method was determined prior and after air-abrasion. Univariate ANOVA followed by post-hoc Scheffé test was computed (p < 0.05). Using Ciba-Geigy tables and chi-square, failure types were analyzed. The DC values were >85% after all cleaning methods, with centrifugation showing the lowest. CCP pretreatment exhibited the lowest TBS values, with predominantly adhesive failures. The combination of CCP and centrifugation increased the TBS values (p < 0.001) compared to the chemical cleaning. CUB, SUP, and VL, regardless of cleaning, can increase the bond strength between the 3D printed resin and the conventional luting resin. Full article

(This article belongs to the Special Issue Additive Manufacturing of Polymers: Materials and Applications)

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16 pages, 6346 KiB

Open AccessArticle

Comparison of Ultrasonic Phased Array and Film Radiography in Detection of Artificially Embedded Defects in Welded Plates

by Arijan Herceg, Leon Maglić, Branko Grizelj and Vlatko Marušić

Materials 2023, 16(9), 3579; https://doi.org/10.3390/ma16093579 - 07 May 2023

Viewed by 1380

Abstract

Ultrasonic and radiographic testing are generally two basic methods for volumetric (internal) defect detection in non-destructive testing. Since both methods are commonly used for the same thing, the question arises as to whether both are equally capable of detecting some commonly occurring defects [...] Read more.

Ultrasonic and radiographic testing are generally two basic methods for volumetric (internal) defect detection in non-destructive testing. Since both methods are commonly used for the same thing, the question arises as to whether both are equally capable of detecting some commonly occurring defects in manufacturing. Commonly occurring defects are generally considered to be fusion defects, drilled holes (which act as pores), etc. To prove or disprove the hypothesis that both methods can generally be used to detect these defects, an experiment was conducted using three welded plates with artificially inserted defects. The welded plates had multiple defects that were intentionally placed close to each other to further complicate the interpretation of the UT results. UT investigation was based on phased-array technology with a multi-element probe. RT investigation was performed with an X-ray machine. Both investigations were based on the respective European standards: for UT, EN ISO 17640, and for RT, EN ISO 17636-1. The results and conclusions from the experiment are presented in this paper. Full article

(This article belongs to the Special Issue Welding Technologies in Materials: Numerical Investigation, Mechanism, Experiment)

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16 pages, 13790 KiB

Open AccessArticle

Study on Austenite Transformation and Growth Evolution of HSLA Steel

by Lu Wang and Shaoyang Wang

Materials 2023, 16(9), 3578; https://doi.org/10.3390/ma16093578 - 07 May 2023

Cited by 2 | Viewed by 1249

Abstract

HSLA steel is widely used in various applications for its excellent mechanical properties. The evolution of austenite transformation and growth has been systematically studied in HSLA steel Q960 during the heating process. A thermal expansion instrument and optical microscope were adopted to analyze [...] Read more.

HSLA steel is widely used in various applications for its excellent mechanical properties. The evolution of austenite transformation and growth has been systematically studied in HSLA steel Q960 during the heating process. A thermal expansion instrument and optical microscope were adopted to analyze the kinetics of austenite transformation, which is a nonlinear continuous process and was accurately calculated by the lever rule based on the dilatation curve at the holding time within 10 min. The austenite growth behavior at temperatures above A_c3 was explored using TEM and DSC. The main precipitates in austenite were Nb-rich and Ti-rich (Nb, Ti)(C, N), and the particle size increased and amount decreased with the increase in the heating temperature, which resulted in the rapid growth of austenite. With the increase in holding temperature and time, the growth of austenite progressed through three stages, and a heat treatment diagram was established to describe this evolution. Full article

(This article belongs to the Special Issue Heat Treatment of Metallic Materials in Modern Industry)

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15 pages, 4424 KiB

Open AccessArticle

Highly Efficient NO₂ Sensors Based on Al-ZnOHF under UV Assistance

by Xingyu Yao, Rutao Wang, Lili Wu, Haixiang Song, Jinbo Zhao, Fei Liu, Kaili Fu, Zhou Wang, Fenglong Wang and Jiurong Liu

Materials 2023, 16(9), 3577; https://doi.org/10.3390/ma16093577 - 07 May 2023

Cited by 1 | Viewed by 1128

Abstract

Zinc hydroxyfluoride (ZnOHF) is a newly found resistive semiconductor used as a gas-sensing material with excellent selectivity to NO₂ because of its unique energy band structure. In this paper, Al³⁺ doping and UV radiation were used to further improve the gas-sensing [...] Read more.

Zinc hydroxyfluoride (ZnOHF) is a newly found resistive semiconductor used as a gas-sensing material with excellent selectivity to NO₂ because of its unique energy band structure. In this paper, Al³⁺ doping and UV radiation were used to further improve the gas-sensing performance of ZnOHF. The optimized 0.5 at.% Al-ZnOHF sample exhibits improved sensitivity to 10 ppm NO₂ at a lower temperature (100 °C) under UV assistance, as well as a short response/recovery time (35 s/96 s). The gas-sensing mechanism demonstrates that Al³⁺ doping increases electron concentration and promotes electron transfer of the nanorods by reducing the bandgap of ZnOHF, and the photogenerated electrons and holes with high activity under UV irradiation provide new reaction routes in the gas adsorption and desorption process, effectively promoting the gas-sensing process. The synergistic effect of Al³⁺ and UV radiation contribute to the enhanced performance of Al-ZnOHF. Full article

(This article belongs to the Special Issue Application of Emerging Materials for Advanced Imaging and Sensing)

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19 pages, 5907 KiB

Open AccessArticle

Experimental Investigation on the Influence of Crack Width of Asphalt Concrete on the Repair Effect of Microbially Induced Calcite Precipitation

by Ling Fan, Jinghong Zheng, Shuquan Peng, Zhize Xun and Guoliang Chen

Materials 2023, 16(9), 3576; https://doi.org/10.3390/ma16093576 - 07 May 2023

Cited by 2 | Viewed by 1265

Abstract

The appearance of cracks is one of the reasons that affect the performance of asphalt pavement, and traditional repair methods have the potential problem of causing adverse effects on the environment. In this paper, an environmentally friendly method for asphalt concrete crack repair [...] Read more.

The appearance of cracks is one of the reasons that affect the performance of asphalt pavement, and traditional repair methods have the potential problem of causing adverse effects on the environment. In this paper, an environmentally friendly method for asphalt concrete crack repair was investigated using microbially induced calcite precipitation (MICP) for asphalt concrete cracks of different widths (0.5 mm, 1.0 mm, 1.5 mm, and 3 mm), and the effectiveness of repair was evaluated using nondestructive and destructive experiments. A varied ultrasonic pulse velocity was used to evaluate the healing process, and it was found that the samples with an initial crack width of 0.5 mm showed the most significant increase in wave velocity of 18.06% after repair. The results also showed that the uniaxial compressive strength and indirect tensile strength of the MICP-repaired samples recovered up to 47.02% and 34.68%. Static creep test results showed that MICP-repaired samples with smaller width cracks had greater resistance to permanent deformation. The results of uniaxial compressive strength tests on larger width (3 mm) cracks repaired by MICP combined with fibers showed that the strength of the samples was significantly increased by the addition of fibers. In addition, the SEM/EDS results showed that the MICP products were spherical calcite particles with a particle size distribution from 0 to 10 μm. This study shows that MICP has some potential for repairing cracks in asphalt concrete of different widths within the range investigated. Full article

(This article belongs to the Special Issue Green and Sustainable Infrastructure Construction Materials)

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