Materials

15 pages, 5661 KiB

Open AccessArticle

Ni-Al Bronze in Molten Carbonate Manufactured by LPBF: Effect of Porosity Design on Mechanical Properties and Oxidation

by Camila Arcos, Carolina Guerra, Jorge A. Ramos-Grez and Mamié Sancy

Materials 2023, 16(10), 3893; https://doi.org/10.3390/ma16103893 - 22 May 2023

Cited by 3 | Viewed by 1195

Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel–aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and [...] Read more.

Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel–aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and thermal treatment on mechanical and chemical stability in molten carbonate (Li₂CO₃-K₂CO₃). Micrographs showed a typical morphology of the martensite phase for all samples in as-built conditions and a spheroid structure on the surface after the heat treatment, possibly revealing the formation of molten salt deposits and corrosion products. FE-SEM analysis of the bulk samples showed some pores with a diameter near 2–5 μm in the as-built condition, which varied between 100 and −1000 μm for the porous samples. After exposure, the cross-section images of porous samples revealed a film composed principally of Cu and Fe, Al, followed by a Ni-rich zone, whose thickness was approximately 1.5 µm, which depended on the porous design but was not influenced significantly by the heat treatment. Additionally, by incorporating porosity, the corrosion rate of NAB samples increased slightly. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys)

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16 pages, 5715 KiB

Open AccessArticle

Development of an Instantaneous Loading Impact Test System for Containment of a Nuclear Power Plant during Aircraft Impact on Steel Bar Joints

by Wanxu Zhu, Shiyuan Liang, Kefei Jia, Quanxi Shen and Dongwen Wu

Materials 2023, 16(10), 3892; https://doi.org/10.3390/ma16103892 - 22 May 2023

Viewed by 1431

Abstract

As major projects such as nuclear power plants continuously increase, it is inevitable that loopholes will arise in safety precautions. Airplane anchoring structures, comprising steel joints and acting as a key component of such a major project, directly affect the safety of the [...] Read more.

As major projects such as nuclear power plants continuously increase, it is inevitable that loopholes will arise in safety precautions. Airplane anchoring structures, comprising steel joints and acting as a key component of such a major project, directly affect the safety of the project due to their resistance to the instant impact of an airplane. Existing impact testing machines have the limitations of being unable to balance impact velocity and impact force, as well as having inadequate control of impact velocity; they cannot meet the requirements of impact testing for steel mechanical connections in nuclear power plants. This paper discusses the hydraulic-based principle of the impact test system, adopts the hydraulic control mode, and uses the accumulator as the power source to develop an instant loading test system suitable for the entire series of steel joints and small-scale cable impact tests. The system is equipped with a 2000 kN static-pressure-supported high-speed servo linear actuator, a 2 × 22 kW oil pump motor group, a 2.2 kW high-pressure oil pump motor group, and a 9000 L/min nitrogen-charging accumulator group, which can test the impact of large-tonnage instant tensile loading. The maximum impact force of the system is 2000 kN, and the maximum impact rate is 1.5 m/s. Through the impact testing of mechanical connecting components using the developed impact test system, it was found that the strain rate of the specimen before failure was not less than 1 s⁻¹, meeting the requirements of the technical specifications for nuclear power plants. By adjusting the working pressure of the accumulator group, the impact rate could be controlled effectively, thus providing a strong experimental platform for research in the field of engineering for preventing emergencies. Full article

(This article belongs to the Special Issue Manufacturing Technology, Materials and Methods)

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27 pages, 12080 KiB

Open AccessArticle

Multi-Response Optimization of High-Performance Low-pH Grouting Materials by Using Taguchi-Based Grey Relational Analysis

by Zengzeng Ren, Weiquan Zhao, Ju Wang, Jinjie Zhang, Liang Chen and Yonghui Li

Materials 2023, 16(10), 3891; https://doi.org/10.3390/ma16103891 - 22 May 2023

Viewed by 1158

Abstract

The most accepted approach to sealing in high-level radioactive waste repositories (HLRWs) is to develop a low-pH grouting material with a pH of the pore solution of less than 11. Currently, the most widely used binary low-pH grouting material is MCSF64, which comprises [...] Read more.

The most accepted approach to sealing in high-level radioactive waste repositories (HLRWs) is to develop a low-pH grouting material with a pH of the pore solution of less than 11. Currently, the most widely used binary low-pH grouting material is MCSF64, which comprises 60% microfine cement (MC) and 40% silica fume (SF). In this study, a high-performance MCSF64-based grouting material was developed by incorporating naphthalene superplasticizer (NSP), aluminum sulfate (AS), and united expansion agent (UEA) to enhance the slurry’s shear strength, compressive strength, and hydration process. Orthogonal experiments were conducted to measure the flow time, yield stress, plastic viscosity, initial setting time, shear strength, and compressive strength of the MCSF64-based slurry, and the optimal mix proportion was determined using the Taguchi–Grey relational analysis method. The pH variation of the pore solution, shrinkage/expansion, and hydration products of the optimal hardened slurry were evaluated using simplified ex-situ leaching (S-ESL), a length comparometer, and scanning electron microscopy (SEM), respectively. The results demonstrate that the Bingham model effectively predicted the rheological properties of the MCSF64-based slurry. The optimum ratio for the MCSF64-based slurry was water/binder (W/B) ratio of 1.4, and the contents of NSP, AS and UEA by mass of binder were 1.9%, 3.6% and 4.8%, respectively. The optimal mix exhibited a pH value below 11 after curing for 120 days. The addition of AS and UEA facilitated hydration, shortened the initial setting time, improved early shear strength, and enhanced the expansion ability of the optimal mix under water curing conditions. Full article

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17 pages, 2079 KiB

Open AccessArticle

Microscopic and Mechanical Characterization of Co-Cr Dental Alloys Joined by the TIG Welding Process

by Andreja Carek, Ljerka Slokar Benić, Vatroslav Bubalo and Nika Kosović

Materials 2023, 16(10), 3890; https://doi.org/10.3390/ma16103890 - 22 May 2023

Cited by 1 | Viewed by 989

Abstract

Due to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas [...] Read more.

Due to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas welding (TIG) produces a high-quality weld with a composition very close to that of the base material. Therefore, in this work, six commercially available Co-Cr dental alloys were joined by TIG welding, and their mechanical properties were evaluated to determine the quality of the TIG process as a technology for joining metallic dental materials and the suitability of the Co-Cr alloys used for TIG welding. Microscopic observations were made for this purpose. Microhardness was measured using the Vickers method. The flexural strength was determined on a mechanical testing machine. The dynamic tests were carried out on a universal testing machine. The mechanical properties were determined for welded and non-welded specimens, and the results were statistically evaluated. The results show the correlation between the investigated mechanical properties and the process TIG. Indeed, characteristics of the welds have an effect on the measured properties. Considering all the results obtained, the TIG—welded I—BOND NF and Wisil M alloys showed the cleanest and most uniform weld and, accordingly, satisfactory mechanical properties, highlighting that they withstood the maximum number of cycles under dynamic load. Full article

(This article belongs to the Section Biomaterials)

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28 pages, 16046 KiB

Open AccessArticle

Analysis of the Effect of Protective Properties of Concretes with Similar Composition on the Corrosion Rate of Reinforcing Steel Induced by Chloride Ions

by Zofia Szweda, Justyna Kuziak, Liwia Sozańska-Jędrasik and Dominik Czachura

Materials 2023, 16(10), 3889; https://doi.org/10.3390/ma16103889 - 22 May 2023

Cited by 2 | Viewed by 1061

Abstract

This study presents a comparison of the protective properties of three concretes of similar composition on the effect of chloride ions. To determine these properties, the values of the diffusion and migration coefficients of chloride ions in concrete were determined using both standard [...] Read more.

This study presents a comparison of the protective properties of three concretes of similar composition on the effect of chloride ions. To determine these properties, the values of the diffusion and migration coefficients of chloride ions in concrete were determined using both standard methods and the thermodynamic ion migration model. We tested a comprehensive method for checking the protective properties of concrete against chlorides. This method can not only be used in various concretes, even those with only small differences in composition, but also in concretes with various types of admixtures and additives, such as PVA fibers. The research was carried out to address the needs of a manufacturer of prefabricated concrete foundations. The aim was to find a cheap and effective method of sealing the concrete produced by the manufacturer in order to carry out projects in coastal areas. Earlier diffusion studies showed good performance when replacing ordinary CEM I cement with metallurgical cement. The corrosion rates of the reinforcing steel in these concretes were also compared using the following electrochemical methods: linear polarization and impedance spectroscopy. The porosities of these concretes, determined using X-ray computed tomography for pore-related characterization, were also compared. Changes in the phase composition of corrosion products occurring in the steel–concrete contact zone were compared using scanning electron microscopy with a micro-area chemical analysis capability, in addition to X-ray microdiffraction, to study the microstructure changes. Concrete with CEM III cement was the most resistant to chloride ingress and therefore provided the longest period of protection against chloride-initiated corrosion. The least resistant was concrete with CEM I, for which, after two 7-day cycles of chloride migration in the electric field, steel corrosion started. The additional use of a sealing admixture can cause a local increase in the volume of pores in the concrete, and at the same time, a local weakening of the concrete structure. Concrete with CEM I was characterized as having the highest porosity at 140.537 pores, whereas concrete with CEM III (characterized by lower porosity) had 123.015 pores. Concrete with sealing admixture, with the same open porosity, had the highest number of pores, at 174.880. According to the findings of this study, and using a computed tomography method, concrete with CEM III showed the most uniform distribution of pores of different volumes, and had the lowest total number of pores. Full article

(This article belongs to the Special Issue Microstructure, Characteristics, and Failure Behaviors of Cementitious Composites)

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16 pages, 7655 KiB

Open AccessArticle

Maximizing the Recycling of Iron Ore Pellets Fines Using Innovative Organic Binders

by Karthik Manu, Elsayed Mousa, Hesham Ahmed, Mohamed Elsadek and Weihong Yang

Materials 2023, 16(10), 3888; https://doi.org/10.3390/ma16103888 - 22 May 2023

Cited by 3 | Viewed by 1533

Abstract

This research work focuses on the practicality of using organic binders for the briquetting of pellet fines. The developed briquettes were evaluated in terms of mechanical strength and reduction behavior with hydrogen. A hydraulic compression testing machine and thermogravimetric analysis were incorporated into [...] Read more.

This research work focuses on the practicality of using organic binders for the briquetting of pellet fines. The developed briquettes were evaluated in terms of mechanical strength and reduction behavior with hydrogen. A hydraulic compression testing machine and thermogravimetric analysis were incorporated into this work to investigate the mechanical strength and reduction behavior of the produced briquettes. Six organic binders, namely Kempel, lignin, starch, lignosulfonate, Alcotac CB6, and Alcotac FE14, in addition to sodium silicate, were tested for the briquetting of pellet fines. The highest mechanical strength was achieved using sodium silicate, Kempel, CB6, and lignosulfonate. The best combination of binder to attain the required mechanical strength even after 100% reduction was found to be a combination of 1.5 wt.% of organic binder (either CB6 or Kempel) with 0.5 wt.% of inorganic binder (sodium silicate). Upscaling using an extruder gave propitious results in the reduction behavior, as the produced briquettes were highly porous and attained pre-requisite mechanical strength. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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12 pages, 7663 KiB

Open AccessArticle

The Influence of MSR-B Mg Alloy Surface Preparation on Bonding Properties

by Katarzyna Łyczkowska, Damian Miara, Beata Rams, Janusz Adamiec and Katarzyna Baluch

Materials 2023, 16(10), 3887; https://doi.org/10.3390/ma16103887 - 22 May 2023

Viewed by 1033

Abstract

Nowadays, industrial adhesives are replacing conventional bonding methods in many industries, including the automotive, aviation, and power industries, among others. The continuous development of joining technology has promoted adhesive bonding as one of the basic methods of joining metal materials. This article presents [...] Read more.

Nowadays, industrial adhesives are replacing conventional bonding methods in many industries, including the automotive, aviation, and power industries, among others. The continuous development of joining technology has promoted adhesive bonding as one of the basic methods of joining metal materials. This article presents the influence of surface preparation of magnesium alloys on the strength properties of a single-lap adhesive joint using a one-component epoxy adhesive. The samples were subjected to shear strength tests and metallographic observations. The lowest properties of the adhesive joint were obtained on samples degreased with isopropyl alcohol. The lack of surface treatment before joining led to destruction by adhesive and mixed mechanisms. Higher properties were obtained for samples ground with sandpaper. The depressions created as a result of grinding increased the contact area of the adhesive with the magnesium alloys. The highest properties were noticed for samples after sandblasting. This proved that the development of the surface layer and the formation of larger grooves increased both the shear strength and the resistance of the adhesive bonding to fracture toughness. It was found that the method of surface preparation had a significant influence on the resulting failure mechanism, and the adhesive bonding of the casting of magnesium alloy QE22 can be used successfully. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys)

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16 pages, 14288 KiB

Open AccessArticle

Improvement of Hot Tearing Resistance of AZ91 Alloy with the Addition of Trace Ca

by Hongchen Xiang, Wenjun Liu, Qiang Wang, Bin Jiang, Jiangfeng Song, Hang Wu, Nan Feng and Linjiang Chai

Materials 2023, 16(10), 3886; https://doi.org/10.3390/ma16103886 - 22 May 2023

Viewed by 1049

Abstract

Hot tearing is the most common and serious casting defect that restricts the light weight and integration of magnesium alloy components. In the present study, trace Ca (0–1.0 wt.%) was added to improve the resistance of AZ91 alloy to hot tearing. The hot [...] Read more.

Hot tearing is the most common and serious casting defect that restricts the light weight and integration of magnesium alloy components. In the present study, trace Ca (0–1.0 wt.%) was added to improve the resistance of AZ91 alloy to hot tearing. The hot tearing susceptivity (HTS) of alloys was experimentally measured by a constraint rod casting method. The results indicate that the HTS presents a ν-shaped tendency with the increase in Ca content, and reaches its minimum value in AZ91–0.1Ca alloy. Ca is well dissolved into α-Mg matrix and Mg₁₇Al₁₂ phase at an addition not exceeding 0.1 wt.%. The solid-solution behavior of Ca increases eutectic content and its corresponding liquid film thickness, improves the strength of dendrites at high temperature, and thereby promotes the hot tearing resistance of the alloy. Al₂Ca phases appear and aggregate at dendrite boundaries with further increases in Ca above 0.1 wt.%. The coarsened Al₂Ca phase hinders the feeding channel and causes stress concentration during the solidification shrinkage, thereby deteriorating the hot tearing resistance of the alloy. These findings were further verified by fracture morphology observations and microscopic strain analysis near the fracture surface based on kernel average misorientation (KAM). Full article

(This article belongs to the Special Issue Metallic Materials: Microstructure, Phase Equilibria and Thermodynamics)

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16 pages, 10928 KiB

Open AccessArticle

Microstructural Changes Caused by the Creep Test in ZK60 Alloy Reinforced by SiC_p at Intermediate Temperature after KOBO Extrusion and Aging

by Yang-Yang Wang, Chen Jia, Min Xu, Mosab Kaseem and Morteza Tayebi

Materials 2023, 16(10), 3885; https://doi.org/10.3390/ma16103885 - 22 May 2023

Cited by 6 | Viewed by 1150

Abstract

In this study, we investigated the creep properties of ZK60 alloy and a ZK60/SiC_p composite at 200 °C and 250 °C in the 10–80 MPa stress range after the KOBO extrusion and precipitation hardening process. The true stress exponent was obtained in [...] Read more.

In this study, we investigated the creep properties of ZK60 alloy and a ZK60/SiC_p composite at 200 °C and 250 °C in the 10–80 MPa stress range after the KOBO extrusion and precipitation hardening process. The true stress exponent was obtained in the range of 1.6–2.3 for both the unreinforced alloy and the composite. The apparent activation energy of the unreinforced alloy was found to be in the range of 80.91–88.09 kJ/mol, and that of the composite was found to be in the range of 47.15–81.60 kJ/mol, and this indicated the grain boundary sliding (GBS) mechanism. An investigation of crept microstructures using an optical microscope and scanning electron microscope (SEM) showed that at 200 °C, the predominant strengthening mechanisms at low stresses were the formation of twin, double twin, and shear bands, and that by increasing the stress, kink bands were activated. At 250 °C, it was found that a slip band was created in the microstructure, and this effectively delayed GBS. The failure surfaces and adjacent regions were examined using SEM, and it was discovered that the primary cause of failure was cavity nucleation around precipitations and reinforcement particles. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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29 pages, 1691 KiB

Open AccessArticle

A Novelty Procedure to Identify Critical Causes of Materials Incompatibility

by Dominika Siwiec, Jacek Pacana and Andrzej Pacana

Materials 2023, 16(10), 3884; https://doi.org/10.3390/ma16103884 - 22 May 2023

Cited by 4 | Viewed by 924

Abstract

Ensuring the expected quality of materials is still a challenge, mainly in order to precisely plan improvement actions that allow for stabilization of the production process. Therefore, the purpose of this research was to develop a novel procedure to identify critical causes of [...] Read more.

Ensuring the expected quality of materials is still a challenge, mainly in order to precisely plan improvement actions that allow for stabilization of the production process. Therefore, the purpose of this research was to develop a novel procedure to identify critical causes of material incompatibility—the causes that have the largest negative impact on material deterioration, and the natural environment. The main originality of this procedure is developing a way to coherent analyse the mutual influence of the many causes of incompatibility of any material, after which the critical causes are identified and a ranking of improvement actions to eliminate these causes is created. A novelty is also developed in the algorithm supporting this procedure, which can be realized in three different ways to solve this problem, i.e.; by considering the impact of material incompatibility on: (i) the deterioration of the material quality; (ii) the deterioration of the natural environment; and (iii) simultaneously the deterioration of the quality of the material and the natural environment. The effectiveness of this procedure was confirmed after tests on 410 alloy, from which a mechanical seal was made. However, this procedure can be useful for any material or industrial product. Full article

(This article belongs to the Special Issue Materials and Processes for Sustainable Energy and Environmental Systems, Volume II)

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15 pages, 3656 KiB

Open AccessArticle

Diatomites from the Iberian Peninsula as Pozzolans

by Jorge L. Costafreda, Domingo A. Martín, Beatriz Astudillo, Leticia Presa, José Luis Parra and Miguel A. Sanjuán

Materials 2023, 16(10), 3883; https://doi.org/10.3390/ma16103883 - 22 May 2023

Cited by 1 | Viewed by 815

Abstract

The object of this work is to study and characterize diatomites from the southeast of the Iberian Peninsula to establish their character and quality as natural pozzolans. This research carried out a morphological and chemical characterization study of the samples using SEM and [...] Read more.

The object of this work is to study and characterize diatomites from the southeast of the Iberian Peninsula to establish their character and quality as natural pozzolans. This research carried out a morphological and chemical characterization study of the samples using SEM and XRF. Subsequently, the physical properties of the samples were determined, including thermic treatment, Blaine particle finesse, real density and apparent density, porosity, volume stability, and the initial and final setting times. Finally, a detailed study was conducted to establish the technical properties of the samples through chemical analysis of technological quality, chemical analysis of pozzolanicity, mechanical compressive strength tests at 7, 28, and 90 days, and a non-destructive ultrasonic pulse test. The results using SEM and XRF show that the samples are composed entirely of colonies of diatoms whose bodies are formed by silica between 83.8 and 89.99% and CaO between 5.2 and 5.8%. Likewise, this indicates a remarkable reactivity of the SiO₂ present in both natural diatomite (~99.4%) and calcined diatomite (~99.2%), respectively. Sulfates and chlorides are absent, while the insoluble residue portion for natural diatomite is 1.54% and 1.92% for calcined diatomite, values comparatively lower than the standardized 3%. On the other hand, the results of the chemical analysis of pozzolanicity show that the samples studied behave efficiently as natural pozzolans, both in a natural and calcined state. The mechanical tests establish that the mechanical strength of the mixed Portland cement and natural diatomite specimens (52.5 MPa) with 10% PC substitution exceeds the reference specimen (51.9 MPa) after 28 days of curing. In the case of the specimens made with Portland cement and calcined diatomite (10%), the compressive strength values increase even more and exceed the reference specimen at both 28 days (54 MPa) and 90 days (64.5 MPa) of curing. The results obtained in this research confirm that the diatomites studied are pozzolanic, which is of vital importance because they could be used to improve cements, mortars, and concrete, which translates to a positive advantage in the care of the environment. Full article

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14 pages, 2420 KiB

Open AccessEditor’s ChoiceArticle

Construction of Bio-TiO₂/Algae Complex and Synergetic Mechanism of the Acceleration of Phenol Biodegradation

by Jinxin Guo, Xiaoman Guo, Haiyan Yang, Daohong Zhang and Xiaogeng Jiang

Materials 2023, 16(10), 3882; https://doi.org/10.3390/ma16103882 - 22 May 2023

Cited by 1 | Viewed by 1030

Abstract

Microalgae have been widely employed in water pollution treatment since they are eco-friendly and economical. However, the relatively slow treatment rate and low toxic tolerance have seriously limited their utilization in numerous conditions. In light of the problems above, a novel biosynthetic titanium [...] Read more.

Microalgae have been widely employed in water pollution treatment since they are eco-friendly and economical. However, the relatively slow treatment rate and low toxic tolerance have seriously limited their utilization in numerous conditions. In light of the problems above, a novel biosynthetic titanium dioxide (bio-TiO₂ NPs)—microalgae synergetic system (Bio-TiO₂/Algae complex) has been established and adopted for phenol degradation in the study. The great biocompatibility of bio-TiO₂ NPs ensured the collaboration with microalgae, improving the phenol degradation rate by 2.27 times compared to that with single microalgae. Remarkably, this system increased the toxicity tolerance of microalgae, represented as promoted extracellular polymeric substances EPS secretion (5.79 times than single algae), and significantly reduced the levels of malondialdehyde and superoxide dismutase. The boosted phenol biodegradation with Bio-TiO₂/Algae complex may be attributed to the synergetic interaction of bio-TiO₂ NPs and microalgae, which led to the decreased bandgap, suppressed recombination rate, and accelerated electron transfer (showed as low electron transfer resistance, larger capacitance, and higher exchange current density), resulting in increased light energy utilization rate and photocatalytic rate. The results of the work provide a new understanding of the low-carbon treatment of toxic organic wastewater and lay a foundation for further remediation application. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts for Biomass Conversion and Environmental Remediation)

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18 pages, 38592 KiB

Open AccessArticle

Insights into the Mechanism of Graphene Acting on Water and Chloride Ion Permeability of Cement-Based Materials

by Jianmiao Dong, Jiaqiao Zhuang, Wanjin Li, Mingxuan Zou, Qi He and Shuqiong Luo

Materials 2023, 16(10), 3881; https://doi.org/10.3390/ma16103881 - 22 May 2023

Cited by 1 | Viewed by 1006

Abstract

Due to its excellent mechanical properties and high aspect ratio, graphene can significantly improve the water and chloride ion permeability resistance of cementitious materials. However, few studies have investigated the effect of graphene size on the water and chloride ion permeability resistance of [...] Read more.

Due to its excellent mechanical properties and high aspect ratio, graphene can significantly improve the water and chloride ion permeability resistance of cementitious materials. However, few studies have investigated the effect of graphene size on the water and chloride ion permeability resistance of cementitious materials. The main issues are as follows: How do different sizes of graphene affect the water and chloride ion permeability resistance of cement-based materials, and by what means do they affect these properties? To address these issues, in this paper, two different sizes of graphene were used to prepare graphene dispersion, which was then mixed with cement to make graphene-reinforced cement-based materials. The permeability and microstructure of samples were investigated. Results show that the addition of graphene effectively improved both the water and chloride ion permeability resistance of cement-based materials significantly. The SEM (scanning electron microscope) images and XRD (X-ray diffraction) analysis show that the introduction of either type of graphene could effectively regulate the crystal size and morphology of hydration products and reduce the crystal size and the number of needle-like and rod-like hydration products. The main types of hydrated products are calcium hydroxide, ettringite, etc. The template effect of large-size graphene was more obvious, and a large number of regular flower-like cluster hydration products were formed, which made the structure of cement paste more compact and thus significantly improved the resistance to the penetration of water and chloride ions into the matrix of the concrete. Full article

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13 pages, 5379 KiB

Open AccessArticle

Potassium Ferrite for Biomedical Applications

by João P. F. Carvalho, Tânia Vieira, Jorge Carvalho Silva, Paula I. P. Soares, Nuno M. Ferreira, Carlos O. Amorim, Sílvia Soreto Teixeira and Manuel P. F. Graça

Materials 2023, 16(10), 3880; https://doi.org/10.3390/ma16103880 - 22 May 2023

Cited by 2 | Viewed by 1169

Abstract

Ferrites have been widely studied for their use in the biomedical area, mostly due to their magnetic properties, which gives them the potential to be used in diagnostics, drug delivery, and in treatment with magnetic hyperthermia, for example. In this work, KFeO₂ [...] Read more.

Ferrites have been widely studied for their use in the biomedical area, mostly due to their magnetic properties, which gives them the potential to be used in diagnostics, drug delivery, and in treatment with magnetic hyperthermia, for example. In this work, KFeO₂ particles were synthesized with a proteic sol-gel method using powdered coconut water as a precursor; this method is based on the principles of green chemistry. To improve its properties, the base powder obtained was subjected to multiple heat treatments at temperatures between 350 and 1300 °C. The samples obtained underwent structural, morphological, biocompatibility, and magnetic characterization. The results show that upon raising the heat treatment temperature, not only is the wanted phase detected, but also the secondary phases. To overcome these secondary phases, several different heat treatments were carried out. Using scanning electron microscopy, grains in the micrometric range were observed. Saturation magnetizations between 15.5 and 24.1 emu/g were observed for the samples containing KFeO₂ with an applied field of 50 kOe at 300 K. From cellular compatibility (cytotoxicity) assays, for concentrations up to 5 mg/mL, only the samples treated at 350 °C were cytotoxic. However, the samples containing KFeO₂, while being biocompatible, had low specific absorption rates (1.55–5.76 W/g). Full article

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11 pages, 6180 KiB

Open AccessArticle

Highly Efficient and Exceptionally Durable Photooxidation Properties on Co₃O₄/g-C₃N₄ Surfaces

by Yelin Dai, Ziyi Feng, Kang Zhong, Jianfeng Tian, Guanyu Wu, Qing Liu, Zhaolong Wang, Yingjie Hua, Jinyuan Liu, Hui Xu and Xingwang Zhu

Materials 2023, 16(10), 3879; https://doi.org/10.3390/ma16103879 - 22 May 2023

Cited by 1 | Viewed by 1011

Abstract

Water pollution is a significant social issue that endangers human health. The technology for the photocatalytic degradation of organic pollutants in water can directly utilize solar energy and has a promising future. A novel Co₃O₄/g-C₃N₄ type-II [...] Read more.

Water pollution is a significant social issue that endangers human health. The technology for the photocatalytic degradation of organic pollutants in water can directly utilize solar energy and has a promising future. A novel Co₃O₄/g-C₃N₄ type-II heterojunction material was prepared by hydrothermal and calcination strategies and used for the economical photocatalytic degradation of rhodamine B (RhB) in water. Benefitting the development of type-II heterojunction structure, the separation and transfer of photogenerated electrons and holes in 5% Co₃O₄/g-C₃N₄ photocatalyst was accelerated, leading to a degradation rate 5.8 times higher than that of pure g-C₃N₄. The radical capturing experiments and ESR spectra indicated that the main active species are •O₂⁻ and h⁺. This work will provide possible routes for exploring catalysts with potential for photocatalytic applications. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Materials for Environmental and Energy Applications)

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15 pages, 3843 KiB

Open AccessArticle

Numerical Investigation on the Compressive Behavior of Desert Sand-Based Backfill Material: Parametric Study

by Haitian Yan, Honglin Liu, Guodong Li, Xiangyu Wang and Yinjian Hang

Materials 2023, 16(10), 3878; https://doi.org/10.3390/ma16103878 - 22 May 2023

Cited by 1 | Viewed by 1021

Abstract

As a key node in the promotion of the “Western Development” strategy in Xinjiang, China, the large-scale mining of coal resources is bound to cause a series of ecological and environmental problems, such as surface subsidence. Desert areas are widely distributed in Xinjiang, [...] Read more.

As a key node in the promotion of the “Western Development” strategy in Xinjiang, China, the large-scale mining of coal resources is bound to cause a series of ecological and environmental problems, such as surface subsidence. Desert areas are widely distributed in Xinjiang, and from the perspective of reserves and sustainable development, it is crucial to fully utilize desert sand to make filling materials and predict its mechanical strength. In order to promote the application of High Water Backfill Material (HWBM) in mining engineering, a modified HWBM doped with Xinjiang Kumutage desert sand was used to prepare a desert sand-based backfill material, and its mechanical properties were tested. The discrete element particle flow software PFC3D is used to construct a three-dimensional numerical model of desert sand-based backfill material. The parameters such as sample sand content, porosity, desert sand particle size distribution, and model size are changed to study their impact on the bearing performance and scale effect of desert sand-based backfill materials. The results indicate that a higher content of desert sand can effectively improve the mechanical properties of HWBM specimens. The stress–strain relationship inverted by the numerical model is highly consistent with the measured results of desert sand-based backfill materials. Improving the particle size distribution of desert sand and reducing the porosity of filling materials within a certain range can significantly improve the bearing capacity of desert sand-based backfill materials. The influence of changing the range of microscopic parameters on the compressive strength of desert sand-based backfill materials was analyzed. This study provides a desert sand-based backfill material that meets the requirements of mine filling, and predicts its strength through numerical simulation. Full article

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

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12 pages, 4343 KiB

Open AccessArticle

Fractal Characterization of the Mass Loss of Bronze by Erosion–Corrosion in Seawater

by Alina Bărbulescu

Materials 2023, 16(10), 3877; https://doi.org/10.3390/ma16103877 - 22 May 2023

Viewed by 913

Abstract

The fractal approach is one of the nondestructive techniques for analyzing corrosion’s effects on different materials. This article utilizes it to analyze the erosion–corrosion produced by cavitation on two types of bronze introduced into an ultrasonic cavitation field to investigate the differences between [...] Read more.

The fractal approach is one of the nondestructive techniques for analyzing corrosion’s effects on different materials. This article utilizes it to analyze the erosion–corrosion produced by cavitation on two types of bronze introduced into an ultrasonic cavitation field to investigate the differences between their behavior in saline water. The aim is to check the hypothesis that the fractal/multifractal measures significantly differ for the studied materials that belong to the same class (bronze) as a step in applying fractal techniques to distinguish between two materials. The study emphasizes the multifractal characteristics of both materials. While the fractal dimensions do not significantly differ, the highest multifractal dimensions correspond to the sample of bronze with Sn. Full article

(This article belongs to the Special Issue Mechanical Properties and Corrosion Behavior of Advanced Materials)

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14 pages, 5230 KiB

Open AccessArticle

A Novel Two-Dimensional TiClO as a High-Performance Anode Material for Mg-Ion Batteries: A First-Principles Study

by Songcheng Zhang and Chunsheng Liu

Materials 2023, 16(10), 3876; https://doi.org/10.3390/ma16103876 - 21 May 2023

Cited by 1 | Viewed by 1181

Abstract

Searching for efficient electrode materials with excellent electrochemical performance is of great significance to the development of magnesium-ion batteries (MIBs). Two-dimensional Ti-based materials are appealing for use in MIBs due to their high cycling capability. On the basis of density functional theory (DFT) [...] Read more.

Searching for efficient electrode materials with excellent electrochemical performance is of great significance to the development of magnesium-ion batteries (MIBs). Two-dimensional Ti-based materials are appealing for use in MIBs due to their high cycling capability. On the basis of density functional theory (DFT) calculations, we comprehensively investigate a novel two-dimensional Ti-based material, namely, TiClO monolayer, as a promising anode for MIBs. Monolayer TiClO can be exfoliated from its experimentally known bulk crystal with a moderate cleavage energy of 1.13 J/m². It exhibits intrinsically metallic properties with good energetical, dynamical, mechanical, and thermal stabilities. Remarkably, TiClO monolayer possesses an ultra-high storage capacity (1079 mA h g⁻¹), a low energy barrier (0.41–0.68 eV), and a suitable average open-circuit voltage (0.96 V). The lattice expansion for the TiClO monolayer is slight (<4.3%) during the Mg-ion intercalation. Moreover, bilayer and trilayer TiClO can considerably enhance the Mg binding strength and maintain the quasi-one-dimensional diffusion feature compared with monolayer TiClO. All these properties indicate that TiClO monolayers can be utilized as high-performance anodes for MIBs. Full article

(This article belongs to the Special Issue Two-Dimensional Materials for Energy Conversion and Storage)

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12 pages, 5403 KiB

Open AccessEditor’s ChoiceArticle

Effects of Steel Slag Powder Content and Curing Condition on the Performance of Alkali-Activated Materials Based UHPC Matrix

by Kangyi Shi, Hongyang Deng, Jinxuan Hu, Junqi Zhou, Xinhua Cai and Zhiwei Liu

Materials 2023, 16(10), 3875; https://doi.org/10.3390/ma16103875 - 21 May 2023

Cited by 3 | Viewed by 1422

Abstract

The accumulation of steel slag and other industrial solid wastes has caused serious environmental pollution and resource waste, and the resource utilization of steel slag is imminent. In this paper, alkali-activated ultra-high-performance concrete (AAM-UHPC) was prepared by replacing ground granulated blast furnace slag [...] Read more.

The accumulation of steel slag and other industrial solid wastes has caused serious environmental pollution and resource waste, and the resource utilization of steel slag is imminent. In this paper, alkali-activated ultra-high-performance concrete (AAM-UHPC) was prepared by replacing ground granulated blast furnace slag (GGBFS) powder with different proportions of steel slag powder, and its workability, mechanical properties, curing condition, microstructure, and pore structure were investigated. The results illustrate that the incorporation of steel slag powder can significantly delay the setting time and improve the flowability of AAM-UHPC, making it possible for engineering applications. The mechanical properties of AAM-UHPC showed a tendency to increase and then decrease with the increase in steel slag dosing and reached their best performance at a 30% dosage of steel slag. The maximum compressive strength and flexural strength are 157.1 MPa and 16.32 Mpa, respectively. High-temperature steam or hot water curing at an early age was beneficial to the strength development of AAM-UHPC, but continuous high-temperature, hot, and humid curing would lead to strength inversion. When the dosage of steel slag is 30%, the average pore diameter of the matrix is only 8.43 nm, and the appropriate steel slag dosage can reduce the heat of hydration and refine the pore size distribution, making the matrix denser. Full article

(This article belongs to the Collection Alkali‐Activated Materials for Sustainable Construction)

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12 pages, 3324 KiB

Open AccessArticle

Experiment and Modelling of the Pre-Strain Effect on the Creep Behaviour of P/M Ni-Based Superalloy FGH96

by Hao Wang, Jingyu Zhang, Huashan Shang, Aixue Sha, Yangyang Cheng and Huiling Duan

Materials 2023, 16(10), 3874; https://doi.org/10.3390/ma16103874 - 21 May 2023

Cited by 2 | Viewed by 1053

Abstract

FGH96 is a powder metallurgy Ni-based superalloy used for turbine disks of aero-engines. In the present study, room-temperature pre-tension experiments with various plastic strain were conducted for the P/M FGH96 alloy, and subsequent creep tests were conducted under the test conditions of 700 [...] Read more.

FGH96 is a powder metallurgy Ni-based superalloy used for turbine disks of aero-engines. In the present study, room-temperature pre-tension experiments with various plastic strain were conducted for the P/M FGH96 alloy, and subsequent creep tests were conducted under the test conditions of 700 °C and 690 MPa. The microstructures of the pre-strained specimens after room-temperature pre-strain and after 70 h creep were investigated. A steady-state creep rate model was proposed, considering the micro-twinning mechanism and pre-strain effects. Progressive increases in steady-state creep rate and creep stain within 70 h were found with increasing amounts of pre-strain. Room-temperature pre-tension within 6.04% plastic strain had no obvious influence on the morphology and distribution of γ′ precipitates, although the dislocation density continuously increased with the increase in pre-strains. The increase in the density of mobile dislocations introduced by pre-strain was the main reason for the increase in creep rate. The predicted steady-state creep rates showed good agreement with the experiment data; the creep model proposed in this study could capture the pre-strain effect. Full article

(This article belongs to the Section Metals and Alloys)

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15 pages, 4971 KiB

Open AccessArticle

The Effect of Radial-Shear Rolling Deformation Processing on the Structure and Properties of Zr-2.5Nb Alloy

by Kirill Ozhmegov, Anna Kawalek, Abdrakhman Naizabekov, Evgeniy Panin, Nikita Lutchenko, Sanzhar Sultanbekov, Medet Magzhanov and Alexandr Arbuz

Materials 2023, 16(10), 3873; https://doi.org/10.3390/ma16103873 - 21 May 2023

Cited by 1 | Viewed by 1097

Abstract

The rheological properties of the Zr-2.5Nb alloy by the strain rate range of 0.5–15 s⁻¹ and by the temperature range of 20–770 °C was studied. The dilatometric method for phase states temperature ranges was experimentally determined. A material properties database for computer [...] Read more.

The rheological properties of the Zr-2.5Nb alloy by the strain rate range of 0.5–15 s⁻¹ and by the temperature range of 20–770 °C was studied. The dilatometric method for phase states temperature ranges was experimentally determined. A material properties database for computer FEM simulation regards the indicated temperature-velocity ranges were created. Using this database and DEFORM-3D FEM-softpack, the radial shear rolling complex process numerical simulation was carried out. The contributed conditions for the ultrafine-grained state alloy structure refinement were determined. Based on the simulation results, a full-scale experiment of Zr-2.5Nb rod rolling a on a radial-shear rolling mill RSP-14/40 was carried out. It takes in seven passes from a diameter of 37–20 mm with a total diameter reduction ε = 85%. According to this case simulation data, the total equivalent strain in the most processed peripheral zone 27.5 mm/mm was reached. Due to the complex vortex metal flow, the equivalent strain over the section distribution was uneven with a gradient reducing towards the axial zone. This fact should have a deep effect on the structure change. Changes and structure gradient by sample section EBSD mapping with 2 mm resolution were studied. The microhardness section gradient by the HV 0.5 method was also studied. The axial and central zones of the sample by the TEM method were studied. The rod section structure has an expressed gradient from the formed equiaxed ultrafine-grained (UFG) structure on a few outer millimeters of the peripheral section to the elongated rolling texture in the center of the bar. The work shows the possibility of processing with the gradient structure obtaining and enhanced properties for the Zr-2.5Nb alloy, and a database for this alloy FEM numerical simulations are also presents. Full article

(This article belongs to the Special Issue Advanced Processing Methods for Metals and Their Alloys)

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26 pages, 5036 KiB

Open AccessArticle

Development and Characterization of Thermoformed Bilayer Trays of Paper and Renewable Succinic Acid Derived Biopolyester Blends and Their Application to Preserve Fresh Pasta

by Eva Hernández-García, Marta Pacheco-Romeralo, Pedro Zomeño, Gianluca Viscusi, Francesca Malvano, Giuliana Gorrasi and Sergio Torres-Giner

Materials 2023, 16(10), 3872; https://doi.org/10.3390/ma16103872 - 21 May 2023

Viewed by 1331

Abstract

The present study reports on the development by thermoforming of highly sustainable trays based on a bilayer structure composed of paper substrate and a film made of a blend of partially bio-based poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA). The incorporation [...] Read more.

The present study reports on the development by thermoforming of highly sustainable trays based on a bilayer structure composed of paper substrate and a film made of a blend of partially bio-based poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA). The incorporation of the renewable succinic acid derived biopolyester blend film slightly improved the thermal resistance and tensile strength of paper, whereas its flexural ductility and puncture resistance were notably enhanced. Furthermore, in terms of barrier properties, the incorporation of this biopolymer blend film reduced the water and aroma vapor permeances of paper by two orders of magnitude, while it endowed the paper structure with intermediate oxygen barrier properties. The resultant thermoformed bilayer trays were, thereafter, originally applied to preserve non-thermally treated Italian artisanal fresh pasta, “fusilli calabresi” type, which was stored under refrigeration conditions for 3 weeks. Shelf-life evaluation showed that the application of the PBS–PBSA film on the paper substrate delayed color changes and mold growth for 1 week, as well as reduced drying of fresh pasta, resulting in acceptable physicochemical quality parameters within 9 days of storage. Lastly, overall migration studies performed with two food simulants demonstrated that the newly developed paper/PBS–PBSA trays are safe since these successfully comply with current legislation on plastic materials and articles intended to come into contact with food. Full article

(This article belongs to the Special Issue Recent Advances in Biobased and Biodegradable Polymers)

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17 pages, 5230 KiB

Open AccessArticle

Properties of Alkali-Activated Slag Cement Activated by Weakly Alkaline Activator

by Juan He, Shuya Yu, Guochen Sang, Junhong He, Jie Wang and Zheng Chen

Materials 2023, 16(10), 3871; https://doi.org/10.3390/ma16103871 - 21 May 2023

Cited by 2 | Viewed by 1286

Abstract

Sodium sulfate (Na₂SO₄) and sodium carbonate (Na₂CO₃) are weakly alkaline activators. Alkali-activated slag (AAS) cement prepared with them shows the special advantages of long setting time and low shrinkage, but it shows slow development of [...] Read more.

Sodium sulfate (Na₂SO₄) and sodium carbonate (Na₂CO₃) are weakly alkaline activators. Alkali-activated slag (AAS) cement prepared with them shows the special advantages of long setting time and low shrinkage, but it shows slow development of mechanical properties. In the paper, Na₂SO₄ and Na₂CO₃ were used as activators and compounded with reactive magnesium oxide (MgO) and calcium hydroxide (Ca(OH)₂) to optimize the setting time and mechanical properties. The hydration products and microscopic morphology were also studied using XRD, SEM, and EDS. Furthermore, the production cost and environmental benefits were compared and analyzed. The results show that Ca(OH)₂ is the main influencing factor for setting time. It reacts preferentially with Na₂CO₃ to form CaCO₃, which makes AAS paste lose plasticity rapidly and shortens the setting time, and then produces strength. Na₂SO₄ and Na₂CO₃ are the main influencing factors for flexural and compressive strength, respectively. Suitably high content is beneficial to promote the development of mechanical strength. The interaction of Na₂CO₃ and Ca(OH)₂ shows a great effect on the initial setting time. High content of reactive MgO can shorten the setting time and increase the mechanical strength at 28 days. There are more crystal phases in hydration products. Considering the setting time and mechanical properties, the composition of activators are: 7% Na₂SO₄, 4% Na₂CO₃, 3–5% Ca(OH)₂, and 2–4% reactive MgO. Compared with ordinary Portland cement (OPC) and AAS cement activated by sodium hydroxide (NaOH, NH) and water glass (WG) with the same alkali equivalent, the production cost and energy consumption are greatly reduced. Compared with P·O 42.5 of OPC, CO₂ emission is reduced by 78.1%. AAS cement activated by weakly alkaline activators shows excellent environmental and economic benefits and good mechanical properties. Full article

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

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16 pages, 5148 KiB

Open AccessArticle

Seismic Performance of Precast Short-Limb Shear Wall with the Bundled Connection at Different Axial Compression Ratios

by Gang Chen, Zihao Yu, Xiaohui Zhang, Hailong Yang, Qian Zhang, Jian Feng and Jianguo Cai

Materials 2023, 16(10), 3870; https://doi.org/10.3390/ma16103870 - 21 May 2023

Viewed by 1181

Abstract

In order to investigate the seismic performance of a precast shear wall with a new bundled connection under a high axial compressive ratio, three full-scale precast short-limb shear walls and one full-scale cast-in-place short-limb shear wall were manufactured and loaded under cycling loading. [...] Read more.

In order to investigate the seismic performance of a precast shear wall with a new bundled connection under a high axial compressive ratio, three full-scale precast short-limb shear walls and one full-scale cast-in-place short-limb shear wall were manufactured and loaded under cycling loading. The results show that the precast short-limb shear wall with a new bundled connection has a similar damage mode and crack evolution to the cast-in-place shear wall. Under the same axial compression ratio, the bearing capacity, ductility coefficient, stiffness, and energy dissipation capacity of the precast short-limb shear wall were better, and its seismic performance is related to the axial compression ratio, with the increase of the axial compression ratio. The embedded bellows can limit the cracking of the wall but have little effect on the bearing capacity and stiffness degradation performance. Furthermore, the bond between the vertical steel bars extending into the preformed holes and grouting materials was demonstrated to be reliable, thus ensuring the integrity of the precast specimens. Full article

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15 pages, 6238 KiB

Open AccessArticle

Strategies for the Covalent Anchoring of a BMP-2-Mimetic Peptide to PEEK Surface for Bone Tissue Engineering

by Leonardo Cassari, Annj Zamuner, Grazia Maria Lucia Messina, Martina Marsotto, Hao-chen Chang, Trevor Coward, Chiara Battocchio, Giovanna Iucci, Giovanni Marletta, Lucy Di Silvio and Monica Dettin

Materials 2023, 16(10), 3869; https://doi.org/10.3390/ma16103869 - 21 May 2023

Cited by 2 | Viewed by 1500

Abstract

Researchers in the field of tissue engineering are always searching for new scaffolds for bone repair. Polyetheretherketone (PEEK) is a chemically inert polymer that is insoluble in conventional solvents. PEEK’s great potential in tissue engineering applications arises from its ability to not induce [...] Read more.

Researchers in the field of tissue engineering are always searching for new scaffolds for bone repair. Polyetheretherketone (PEEK) is a chemically inert polymer that is insoluble in conventional solvents. PEEK’s great potential in tissue engineering applications arises from its ability to not induce adverse reactions when in contact with biological tissues and its mechanical properties, which are similar to those of human bone. These exceptional features are limited by the bio-inertness of PEEK, which causes poor osteogenesis on the implant surface. Here, we demonstrated that the covalent grafting of the sequence (48–69) mapped on the BMP-2 growth factor (GBMP1α) significantly enhances the mineralization and gene expression of human osteoblasts. Different chemical methods were employed for covalently grafting the peptide onto 3D-printed PEEK disks: (a) the reaction between PEEK carbonyls and amino-oxy groups inserted in the peptides’ N-terminal sites (oxime chemistry) and (b) the photoactivation of azido groups present in the peptides’ N-terminal sites, which produces nitrene radicals able to react with PEEK surface. The peptide-induced PEEK surface modification was assessed using X-ray photoelectron measurements, while the superficial properties of the functionalized material were analyzed by means of atomic force microscopy and force spectroscopy. Live and dead assays and SEM measurements showed greater cell cover on functionalized samples than the control, without any cytotoxicity induction. Moreover, functionalization improved the rate of cell proliferation and the amount of calcium deposits, as demonstrated by the AlamarBlue™ and alizarin red results, respectively. The effects of GBMP1α on h-osteoblast gene expression were assayed using quantitative real-time polymerase chain reaction. Full article

(This article belongs to the Special Issue Biomaterials and Implant Biocompatibility (Second Volume))

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21 pages, 8639 KiB

Open AccessArticle

Solution for Determining Modulus of Elasticity of Natural Materials Using Vibrations of Non-Uniform Circular Cross-Section Cantilevers

by Jerzy Podgórski and Bartosz Kawecki

Materials 2023, 16(10), 3868; https://doi.org/10.3390/ma16103868 - 21 May 2023

Viewed by 935

Abstract

The article presents an original method for determining the modulus of elasticity of natural materials. A studied solution was based on vibrations of non-uniform circular cross-section cantilevers solved using Bessel functions. The derived equations, together with experimental tests, allowed for calculating the material’s [...] Read more.

The article presents an original method for determining the modulus of elasticity of natural materials. A studied solution was based on vibrations of non-uniform circular cross-section cantilevers solved using Bessel functions. The derived equations, together with experimental tests, allowed for calculating the material’s properties. Assessments were based on the measurement of the free-end oscillations in time using the Digital Image Correlation (DIC) method. They were induced manually and positioned at the end of a cantilever and monitored in time using a fast Vision Research Phantom v12.1 Camera with 1000 fps. GOM Correlate software tools were then used to find increments of deflection on a free end in every frame. It provided us with the ability to make diagrams containing a displacement–time relation. To find natural vibration frequencies, fast Fourier transform (FFT) analyses were conducted. The correctness of the proposed method was compared with a three-point bending test performed on a Zwick/Roell Z2.5 testing machine. The presented solution generates trustworthy results and can provide a method to confirm the elastic properties of natural materials obtained in various experimental tests. Full article

(This article belongs to the Special Issue Natural Fibers: Characterization, Properties and Applications)

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40 pages, 12853 KiB

Open AccessReview

An Overview of the Latest Progress in Internal Surface Finishing of the Additively Manufactured Metallic Components

by Farideh Davoodi, Mohammad Taghian, Giuseppe Carbone, Abdollah Saboori and Luca Iuliano

Materials 2023, 16(10), 3867; https://doi.org/10.3390/ma16103867 - 21 May 2023

Cited by 1 | Viewed by 2266

Abstract

Fast progress in near-net-shape production of parts has attracted vast interest in internal surface finishing. Interest in designing a modern finishing machine to cover the different shapes of workpieces with different materials has risen recently, and the current state of technology cannot satisfy [...] Read more.

Fast progress in near-net-shape production of parts has attracted vast interest in internal surface finishing. Interest in designing a modern finishing machine to cover the different shapes of workpieces with different materials has risen recently, and the current state of technology cannot satisfy the high requirements for finishing internal channels in metal-additive-manufactured parts. Therefore, in this work, an effort has been made to close the current gaps. This literature review aims to trace the development of different non-traditional internal surface finishing methods. For this reason, attention is focused on the working principles, capabilities, and limitations of the most applicable processes, such as internal magnetic abrasive finishing, abrasive flow machining, fluidized bed machining, cavitation abrasive finishing, and electrochemical machining. Thereafter, a comparison is presented based on which models were surveyed in detail, with particular attention to their specifications and methods. The assessment is measured by seven key features, with two selected methods deciding their value for a proper hybrid machine. Full article

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

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17 pages, 7572 KiB

Open AccessArticle

Investigation on Physico Chemical and X-ray Shielding Performance of Zinc Doped Nano-WO₃ Epoxy Composite for Light Weight Lead Free Aprons

by Sanjeevi Palanisami, Vishnu Shankar Dhandapani, Varuna Jayachandran, Elango Muniappan, Dongkyou Park, Byungki Kim and Kalpana Govindasami

Materials 2023, 16(10), 3866; https://doi.org/10.3390/ma16103866 - 20 May 2023

Viewed by 1399

Abstract

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO₃) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO₃ nanoparticles of 20 to 400 nm were [...] Read more.

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO₃) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO₃ nanoparticles of 20 to 400 nm were synthesized by an inexpensive and scalable chemical acid–precipitation method. The prepared nanoparticles were subjected to X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, photoluminescence, high-resolution–transmission electron microscope, scanning electron microscope, and the results showed that doping plays a critical role in influencing the physico-chemical properties. The prepared nanoparticles were used as shielding material in this study, which were dispersed in a non-water soluble durable epoxy resin polymer matrix and the dispersed materials were coated over a rexine cloth using the drop-casting method. The X-ray shielding performance was evaluated by estimating the linear attenuation coefficient (μ), mass attenuation coefficient (μ_m), half value layer (HVL), and X-ray percentage of attenuation. Overall, an improvement in X-ray attenuation in the range of 40–100 kVp was observed for the undoped WO₃ nanoparticles and Zn-doped WO₃ nanoparticles, which was nearly equal to lead oxide-based aprons (reference material). At 40 kVp, the percentage of attenuation of 2% Zn doped WO₃ was 97% which was better than that of other prepared aprons. This study proves that 2% Zn doped WO₃ epoxy composite yields a better particle size distribution, μ_m, and lower HVL value and hence it can be a convenient lead free X-ray shielding apron. Full article

(This article belongs to the Special Issue Nanoarchitectonics in Materials Science)

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19 pages, 14628 KiB

Open AccessArticle

Machining of Triangular Holes in D2 Steel by the Use of Non-Conventional Electrodes in Die-Sinking Electric Discharge Machining

by Madiha Rafaqat, Nadeem Ahmad Mufti, Muhammad Qaiser Saleem, Naveed Ahmed, Ateekh Ur Rehman and Muhammad Asad Ali

Materials 2023, 16(10), 3865; https://doi.org/10.3390/ma16103865 - 20 May 2023

Cited by 3 | Viewed by 1266

Abstract

Electric discharge machining is relatively a slow process in terms of machining time and material removal rate. The presence of overcut and the hole taper angle caused by the excessive tool wear are other challenges in the electric discharge machining die-sinking process. The [...] Read more.

Electric discharge machining is relatively a slow process in terms of machining time and material removal rate. The presence of overcut and the hole taper angle caused by the excessive tool wear are other challenges in the electric discharge machining die-sinking process. The areas of focus to solve these challenges in the performance of electric discharge machines include increasing the rate of material removal, decreasing the rate of tool wear, and reducing the rate of hole taper angle and overcut. Triangular cross-sectional through-holes have been produced in D2 steel through die-sinking electric discharge machining (EDM). Conventionally, the electrode with uniform triangular cross-section throughout the electrode length is used to machine triangular holes. In this study, new designs of electrodes (non-conventional designs) are employed by introducing circular relief angles. For material removal rate (MRR), tool wear rate (TWR), overcut, taper angle, and surface roughness of the machined holes, the machining performance of conventional and unconventional electrode designs is compared. A significant improvement in MRR (32.6% increase) has been achieved by using non-conventional electrode designs. Similarly, the hole quality resulted by non-conventional electrodes is way better than hole quality corresponding to conventional electrode designs, especially in terms of overcut and hole taper angle. A reduction of 20.6% in overcut and a reduction of 72.5% in taper angle can be achieved through newly designed electrodes. Finally, one electrode design has been selected (electrode with 20 degree relief angle) as the most appropriate electrode resulting in better EDM performance in terms of MRR, TWR, overcut, taper angle, and surface roughness of triangular holes. Full article

(This article belongs to the Special Issue Machining and Surface Properties of Steel Parts)

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31 pages, 16945 KiB

Open AccessReview

Nanostructured TiO₂ Arrays for Energy Storage

by Pingyun Si, Zhilong Zheng, Yijie Gu, Chao Geng, Zhizhong Guo, Jiayi Qin and Wei Wen

Materials 2023, 16(10), 3864; https://doi.org/10.3390/ma16103864 - 20 May 2023

Cited by 1 | Viewed by 1981

Abstract

Because of their extensive specific surface area, excellent charge transfer rate, superior chemical stability, low cost, and Earth abundance, nanostructured titanium dioxide (TiO₂) arrays have been thoroughly explored during the past few decades. The synthesis methods for TiO₂ nanoarrays, which [...] Read more.

Because of their extensive specific surface area, excellent charge transfer rate, superior chemical stability, low cost, and Earth abundance, nanostructured titanium dioxide (TiO₂) arrays have been thoroughly explored during the past few decades. The synthesis methods for TiO₂ nanoarrays, which mainly include hydrothermal/solvothermal processes, vapor-based approaches, templated growth, and top-down fabrication techniques, are summarized, and the mechanisms are also discussed. In order to improve their electrochemical performance, several attempts have been conducted to produce TiO₂ nanoarrays with morphologies and sizes that show tremendous promise for energy storage. This paper provides an overview of current developments in the research of TiO₂ nanostructured arrays. Initially, the morphological engineering of TiO₂ materials is discussed, with an emphasis on the various synthetic techniques and associated chemical and physical characteristics. We then give a brief overview of the most recent uses of TiO₂ nanoarrays in the manufacture of batteries and supercapacitors. This paper also highlights the emerging tendencies and difficulties of TiO₂ nanoarrays in different applications. Full article

(This article belongs to the Special Issue Advances in Organic Framework Materials: Syntheses and Applications)

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