Materials

20 pages, 6473 KiB

Open AccessArticle

Fatigue Life Improvement of Weld Beads with Overlap Defects Using Ultrasonic Peening

by Seung-Hyon Song, Chang-Soon Lee, Tae-Hwan Lim, Auezhan Amanov and In-Sik Cho

Materials 2023, 16(1), 463; https://doi.org/10.3390/ma16010463 - 3 Jan 2023

Cited by 4 | Viewed by 4505

Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects [...] Read more.

Welding defects are common during the production of large welded structures. However, few studies have explored methods of compensating for clear welding defects without resorting to re-welding. Here, an ultrasonic peening method to compensate for the deteriorated mechanical properties of overlap weld defects without repair welding was studied. We experimentally investigated changes in the mechanical properties of defective welds before and after ultrasonic peening. The weld specimen with an overlap defect contained a large cavity-type defect inside the weld bead, which significantly reduced the fatigue life. When the surface of the defective test piece was peened, the fatigue life of the weld plate was restored, resulting in an equivalent or higher number of cycles to failure, compared to a specimen with a normal weld. The recovery of mechanical properties was attributed to the effect of surface work hardening by ultrasonic peening and the change in stress distribution. Thus, ultrasonic peening could compensate for the deterioration of mechanical properties such as tensile strength, fatigue life, and elongation due to overlap defects, without resorting to repair welding. Full article

(This article belongs to the Special Issue Damage and Mechanical Properties of Materials)

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19 pages, 2859 KiB

Open AccessArticle

Adsorption–Desorption Behavior of Hydrogen Sulfide Capture on a Modified Activated Carbon Surface

by Nurul Noramelya Zulkefli, Adam Mohd Izhan Noor Azam, Mohd Shahbudin Masdar and Wan Nor Roslam Wan Isahak

Materials 2023, 16(1), 462; https://doi.org/10.3390/ma16010462 - 3 Jan 2023

Cited by 9 | Viewed by 3113

Abstract

Metal-based adsorbents with varying active phase loadings were synthesized to capture hydrogen sulfide (H₂S) from a biogas mimic system. The adsorption–desorption cycles were implemented to ascertain the H₂S captured. All prepared adsorbents were evaluated by nitrogen adsorption, Brunauer–Emmett–Teller surface [...] Read more.

Metal-based adsorbents with varying active phase loadings were synthesized to capture hydrogen sulfide (H₂S) from a biogas mimic system. The adsorption–desorption cycles were implemented to ascertain the H₂S captured. All prepared adsorbents were evaluated by nitrogen adsorption, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. From the results, modified adsorbents, dual chemical mixture (DCM) and a core–shell (CS) had the highest H₂S adsorption performance with a range of 0.92–1.80 mg H₂S/g. After several cycles of heat/N₂ regeneration, the total H₂S adsorption capacity of the DCM adsorbent decreased by 62.1%, whereas the CS adsorbent decreased by only 25%. Meanwhile, the proposed behavioral model for H₂S adsorption–desorption was validated effectively using various analyses throughout the three cycles of adsorption–desorption samples. Moreover, as in this case, the ZnAc₂/ZnO/CAC_OS adsorbents show outstanding performances with 30 cycles of adsorption–desorption compared to only 12 cycles of ZnAc₂/ZnO/CAC_DCM. Thus, this research paper will provide fresh insights into adsorption–desorption behavior through the best adsorbents’ development and the adsorbents’ capability at the highest number of adsorption–desorption cycles. Full article

(This article belongs to the Special Issue Recent Progress in Advanced Adsorption Materials)

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14 pages, 4604 KiB

Open AccessEditor’s ChoiceArticle

Towards Room Temperature Phase Transition of W-Doped VO₂ Thin Films Deposited by Pulsed Laser Deposition: Thermochromic, Surface, and Structural Analysis

by Yannick Bleu, Florent Bourquard, Vincent Barnier, Anne-Sophie Loir, Florence Garrelie and Christophe Donnet

Materials 2023, 16(1), 461; https://doi.org/10.3390/ma16010461 - 3 Jan 2023

Cited by 15 | Viewed by 4151

Abstract

Vanadium dioxide (VO₂) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W [...] Read more.

Vanadium dioxide (VO₂) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W doping on the thermochromic, surface, and nanostructure properties of VO₂ thin film was investigated in the present proof. W-doped VO₂ thin films with different W contents were deposited by pulsed laser deposition (PLD) using V/W (+O₂) and V₂O₅/W multilayers. Rapid thermal annealing at 400–450 °C under oxygen flow was performed to crystallize the as-deposited films. The thermochromic, surface chemistry, structural, and morphological properties of the thin films obtained were investigated. The results showed that the V⁵⁺ was more surface sensitive and W distribution was homogeneous in all samples. Moreover, the V₂O₅ acted as a W diffusion barrier during the annealing stage, whereas the V+O₂ environment favored W surface diffusion. The phase transition temperature gradually decreased with increasing W content with a high efficiency of −26 °C per at. % W. For the highest doping concentration of 1.7 at. %, VO₂ showed room-temperature transition (26 °C) with high luminous transmittance (62%), indicating great potential for optical applications. Full article

(This article belongs to the Special Issue Structural, Morphological, and Optical Properties of Functional Thin Films)

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16 pages, 7472 KiB

Open AccessArticle

The Effect of Non-Measured Points on the Accuracy of the Surface Topography Assessment of Elements 3D Printed Using Selected Additive Technologies

by Paweł Zmarzły, Tomasz Kozior and Damian Gogolewski

Materials 2023, 16(1), 460; https://doi.org/10.3390/ma16010460 - 3 Jan 2023

Cited by 7 | Viewed by 2245

Abstract

The paper presents the results of research aimed at evaluating the surface topography including the analysis of the number of unmeasured points of the samples 3D printed using four additive technologies (i.e., PolyJet Matrix, fused deposition modeling, selective laser sintering, and selective laser [...] Read more.

The paper presents the results of research aimed at evaluating the surface topography including the analysis of the number of unmeasured points of the samples 3D printed using four additive technologies (i.e., PolyJet Matrix, fused deposition modeling, selective laser sintering, and selective laser melting). The samples were made in three variants of location on the printing platform of 3D printers. Measurements of the samples’ surface topography were carried out using a Talysurf CCI Lite optical profilometer and a Talysurf PGI 1230 contact profilometer. The percentage of non-measured points for each sample and the parameters of the surface topography were determined. Then, the non-measured points were complemented and the topography parameters for the corrected surface were recalculated. In addition, to perform comparative measurements, each surface was measured using a contact profilometer Talysurf PGI 1230. Preliminary results of the research showed that the measurement of the surface topography of the samples made using selective laser sintering technology with the Taysurf CCI optical measuring system is very unreliable, as the number of non-measured points for the analyzed samples was higher than 98%. The highest accuracy of optical measurement was obtained for PJM technology and three variants of location on the printing platform of the 3D printer. Full article

(This article belongs to the Special Issue Recent Trends in Roughness Measurement and Data Analysis of Machined Surfaces)

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12 pages, 1550 KiB

Open AccessEditor’s ChoiceArticle

Effect of Blend Composition on Barrier Properties of Insulating Mats Produced from Local Wool and Waste Bast Fibres

by Anna Kicińska-Jakubowska, Jan Broda, Małgorzata Zimniewska, Marcin Bączek and Jerzy Mańkowski

Materials 2023, 16(1), 459; https://doi.org/10.3390/ma16010459 - 3 Jan 2023

Cited by 6 | Viewed by 1975

Abstract

This paper concerns the management of natural waste fibres. The aim of this research was the production of multifunctional acoustic and thermal insulation materials from natural protein and lignocellulosic fibre wastes, according to a circular bioeconomy. For the manufacture of the materials, local [...] Read more.

This paper concerns the management of natural waste fibres. The aim of this research was the production of multifunctional acoustic and thermal insulation materials from natural protein and lignocellulosic fibre wastes, according to a circular bioeconomy. For the manufacture of the materials, local mountain sheep wool and a mixture of bast fibre waste generated by string production were used. Insulating materials in the form of mats produced by the needle-punching technique with different fibre contents were obtained. The basic parameters of the mats, i.e., the thickness, surface weight and air permeability were determined. To assess barrier properties, sound absorption and noise reduction coefficients, as well as thermal resistance and thermal conductivity, were measured. It was shown that the mats exhibit barrier properties in terms of thermal and acoustic insulation related to the composition of the mat. It was found that mats with a higher content of the bast fibres possess a greater ability to absorb sounds, while mats with higher wool contents exhibit better thermal insulation properties. The produced mats can serve as a good alternative to commonly used acoustic and thermal insulating materials. The production of the described materials allows for a reduction in the amount of natural fibre waste and achieves the goal of “zero waste” according to the European Green Deal strategy. Full article

(This article belongs to the Special Issue Advances in Multifunctional Textiles: Materials, Technologies and Production Processes)

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16 pages, 2536 KiB

Open AccessArticle

Simplified Modelling of the Edge Crush Resistance of Multi-Layered Corrugated Board: Experimental and Computational Study

by Tomasz Garbowski, Anna Knitter-Piątkowska and Piotr Winiarski

Materials 2023, 16(1), 458; https://doi.org/10.3390/ma16010458 - 3 Jan 2023

Cited by 3 | Viewed by 2518

Abstract

The edge crush test is the most popular laboratory test in the corrugated packaging industry. It measures the edge crush resistance of a sample in the cross-fiber direction (CD), also known as the ECT index. This parameter is widely used for the specification [...] Read more.

The edge crush test is the most popular laboratory test in the corrugated packaging industry. It measures the edge crush resistance of a sample in the cross-fiber direction (CD), also known as the ECT index. This parameter is widely used for the specification of the board by its producers. It is also utilized in most analytical formulas describing the load capacity of the packaging. On the other hand, the ECT value can be estimated from both analytical and numerical models based on the basic parameters of each constituent paper. Knowing the compressive strength in CD (commonly known as SCT) and the elastic properties of the individual layers, the sample geometry (i.e., the period and height of the corrugated layer), as well as the boundary conditions, the ECT value can be calculated. This is very useful as new boards can be virtually analyzed before being manufactured. In this work, both detailed numerical models based on finite elements (FE) methods and very simple analytical (engineering) models were used for the ECT calculations. All presented models were validated with experimental data. The surprising consistency and high precision of the results obtained with the simplest approach was additionally analyzed in the study. Full article

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9 pages, 811 KiB

Open AccessArticle

Influence of Thickness of Opaque Porcelain and Alloy Color on the Final Color of Porcelain-Fused-to-Metal Restorations

by Alessandro Vichi, Gabriele Corciolani, Michele Carrabba, Alvaro Munoz and Chris Louca

Materials 2023, 16(1), 457; https://doi.org/10.3390/ma16010457 - 3 Jan 2023

Cited by 2 | Viewed by 2212

Abstract

Despite the advent of metal-free solutions, porcelain-fused-to-metal restorations (PFM) are still widely used. Particularly for the latest ceramic systems, scarce information is present in the scientific literature about the ideal opaque layer thickness and the alloy color impact to achieve the desired final [...] Read more.

Despite the advent of metal-free solutions, porcelain-fused-to-metal restorations (PFM) are still widely used. Particularly for the latest ceramic systems, scarce information is present in the scientific literature about the ideal opaque layer thickness and the alloy color impact to achieve the desired final color of PFM restorations. This study aimed to evaluate the influence of opaque thickness variation layered on different metal alloys on the final color of PFM restorations. Opaque porcelain of one metal–ceramic system (VITA VM13) was layered in four different thicknesses (0.10 mm, 0.15 mm, 0.20 mm, and 0.25 mm) on three differently colored dental alloys: a gold–platinum alloy (yellowish), a gold–palladium alloy (light grayish), and a nickel–chromium alloy (dark grayish). The veneering porcelain layered over the opaque was kept constant (Base Dentine 0.45 mm, Transpa Dentine 0.50 mm, and Enamel 0.20 mm). Sixty specimens were fabricated, five samples for each combination of alloy/opaque thickness. The color difference (ΔE) between specimen and reference was measured using a clinical spectrophotometer. The two-way ANOVA revealed that the thickness of both the opaque (p < 0.001) and the metal alloy (p < 0.001) significantly influenced the ΔE values. Gray-colored alloys covered by a 0.10 mm thick opaque layer enabled the closest color match, whereas this occurred for yellow-color alloys covered by a 0.15 mm thick opaque layer. In contrast, the samples covered by a 0.25 mm thick opaque layer obtained the worst ΔE. Full article

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22 pages, 11399 KiB

Open AccessArticle

Fatigue Reliability Characterisation of Effective Strain Damage Model Using Extreme Value Distribution for Road Load Conditions

by Lennie Abdullah, Salvinder Singh Karam Singh, Shahrum Abdullah, Ahmad Kamal Ariffin and Syifa Syuhaidah Meor Zainal

Materials 2023, 16(1), 456; https://doi.org/10.3390/ma16010456 - 3 Jan 2023

Cited by 1 | Viewed by 2484

Abstract

The aim of this paper is to characterise the fatigue reliability for various random strain loads under extreme value distribution while considering the cycle sequence effect condition in fatigue life prediction. The established strain–life models, i.e., Morrow and Smith–Watson–Topper, considered a mean stress [...] Read more.

The aim of this paper is to characterise the fatigue reliability for various random strain loads under extreme value distribution while considering the cycle sequence effect condition in fatigue life prediction. The established strain–life models, i.e., Morrow and Smith–Watson–Topper, considered a mean stress effect and strain amplitude; nevertheless, it excluded the load sequence effect, which involves the fatigue crack closure that is subjected to overload or underload. A FESEM-EDX analysis is conducted to characterise the failure features that occurred on the leaf spring. A finite element is simulated to determine the critical region in order to obtain the strain load behaviour. In addition, the strain signal is captured experimentally at 500 Hz for 100 s under operating conditions for three different road loads based on the critical location obtained from the finite element analysis. The fatigue life correlation shows that the Pearson correlation coefficients are greater than 0.9, which indicates the effective strain damage model is linearly correlated with the strain–life models. The fatigue life data are modelled using extreme value distribution by considering the random strain loads as extreme data. The reliability rate for the fatigue life is reported to be more than 0.59 within the hazard rate range of 9.6 × 10⁻⁸ to 1.2 × 10⁻⁷ based on the mean cycle to the failure point. Hence, the effective strain damage model is proposed for a fatigue reliability assessment under extreme conditions with higher reliability and provides fatigue life prediction when subjected to cycle sequence effects. Full article

(This article belongs to the Special Issue Fatigue Damage and Fracture Mechanics of Materials)

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12 pages, 3006 KiB

Open AccessEditor’s ChoiceArticle

One-Step Synthesis of Sulfur-Doped Nanoporous Carbons from Lignin with Ultra-High Surface Area, Sulfur Content and CO₂ Adsorption Capacity

by Dipendu Saha, Gerassimos Orkoulas and Dean Bates

Materials 2023, 16(1), 455; https://doi.org/10.3390/ma16010455 - 3 Jan 2023

Cited by 6 | Viewed by 2361

Abstract

Lignin is the second-most available biopolymer in nature. In this work, lignin was employed as the carbon precursor for the one-step synthesis of sulfur-doped nanoporous carbons. Sulfur-doped nanoporous carbons have several applications in scientific and technological sectors. In order to synthesize sulfur-doped nanoporous [...] Read more.

Lignin is the second-most available biopolymer in nature. In this work, lignin was employed as the carbon precursor for the one-step synthesis of sulfur-doped nanoporous carbons. Sulfur-doped nanoporous carbons have several applications in scientific and technological sectors. In order to synthesize sulfur-doped nanoporous carbons from lignin, sodium thiosulfate was employed as a sulfurizing agent and potassium hydroxide as the activating agent to create porosity. The resultant carbons were characterized by pore textural properties, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The nanoporous carbons possess BET surface areas of 741–3626 m²/g and a total pore volume of 0.5–1.74 cm³/g. The BET surface area of the carbon was one of the highest that was reported for any carbon-based materials. The sulfur contents of the carbons are 1–12.6 at.%, and the key functionalities include S=C, S-C=O, and SO_x. The adsorption isotherms of three gases, CO₂, CH₄, and N₂, were measured at 298 K, with pressure up to 1 bar. In all the carbons, the adsorbed amount was highest for CO₂, followed by CH₄ and N₂. The equilibrium uptake capacity for CO₂ was as high as ~11 mmol/g at 298 K and 760 torr, which is likely the highest among all the porous carbon-based materials reported so far. Ideally adsorbed solution theory (IAST) was employed to calculate the selectivity for CO₂/N₂, CO₂/CH₄, and CH₄/N₂, and some of the carbons reported a very high selectivity value. The overall results suggest that these carbons can potentially be used for gas separation purposes. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Sustainable Advanced Nanomaterials)

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10 pages, 1934 KiB

Open AccessArticle

Structural, Magnetic and Vibrational Properties of Van Der Waals Ferromagnet CrBr₃ at High Pressure

by Olga Lis, Denis Kozlenko, Sergey Kichanov, Evgenii Lukin, Ivan Zel and Boris Savenko

Materials 2023, 16(1), 454; https://doi.org/10.3390/ma16010454 - 3 Jan 2023

Cited by 6 | Viewed by 2463

Abstract

The crystal and magnetic structures of van der Waals layered ferromagnet Cr

{Br}_{3}

were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6–300 [...] Read more.

The crystal and magnetic structures of van der Waals layered ferromagnet Cr

{Br}_{3}

were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6–300 K, respectively. The vibration spectra of Cr

{Br}_{3}

were studied using Raman spectroscopy at pressures up to 23 GPa at ambient temperature. The anomalous pressure behavior of structural parameters and vibrational modes was observed, associated with a gradual isostructural phase transition in the pressure range 2.5–7 GPa. The Curie temperature T_C reduced rapidly with a pressure coefficient

d T_{C} / d P = - 4.1 (4)

K/GPa. A full suppression of the ferromagnetic state was expected at P_C~8.4 GPa, where onset of the antiferromagnetic spin arrangement or magnetically disordered state may take place. Anomalies in Raman spectra at P~15 GPa point to another possible phase transformation in Cr

{Br}_{3}

, which may be related to the proximity of metallization of this van der Waals ferromagnet. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics)

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17 pages, 5497 KiB

Open AccessArticle

Impact Resistance of a Fiber Metal Laminate Skin Bio-Inspired Composite Sandwich Panel with a Rubber and Foam Dual Core

by Wenping Zhang, Ruonan Li, Quanzhan Yang, Ying Fu and Xiangqing Kong

Materials 2023, 16(1), 453; https://doi.org/10.3390/ma16010453 - 3 Jan 2023

Cited by 8 | Viewed by 2434

Abstract

This paper reports the development of a novel bio-inspired composite sandwich panel (BCSP) with fiber metal laminate (FML) face sheets and a dual core to improve the low-velocity impact behavior based on the woodpecker’s head layout as a design template. The dynamic response [...] Read more.

This paper reports the development of a novel bio-inspired composite sandwich panel (BCSP) with fiber metal laminate (FML) face sheets and a dual core to improve the low-velocity impact behavior based on the woodpecker’s head layout as a design template. The dynamic response of BCSP under impact load is simulated and analyzed by ABAQUS/Explicit software and compared with that of the composite sandwich panel (CSP) with a single foam core. The impact behavior of BCSP affected by these parameters, i.e., a different face sheet thickness, rubber core thickness and foam core height, was also reported. The results show that BCSP has superior impact resistance compared to CSP, with a lower damage area and smaller deformation, while carrying a higher impact load. Concurrently, BCSP is not highly restricted to any particular region when dealing with stress distributions. Compared to CSP, the bottom skin maximum stress value of BCSP is significantly reduced by 2.4–6.3 times at all considered impact energy levels. It is also found that the impact efficiency index of BCSP is 4.86 times higher than that of CSP under the same impact energy, indicating that the former can resist the impact load more effectively than the latter in terms of overall performance. Furthermore, the impact resistance of the BCSP improved with the increase in face sheet thickness and rubber core thickness. Additionally, the height of the foam core has a notable effect on the energy absorption, while it does not play a significant role in impact load. From an economic viewpoint, the height of the foam core retrofitted with 20 mm is reasonable. The results acquired from the current investigation can provide certain theoretical reference to the use of the bio-inspired composite sandwich panel in the engineering protection field. Full article

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

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16 pages, 8207 KiB

Open AccessArticle

Durability Performance and Corrosion Mechanism of New Basalt Fiber Concrete under Organic Water Environment

by Jun Wei, Zhenshan Wang, Weidong Sun and Runan Yang

Materials 2023, 16(1), 452; https://doi.org/10.3390/ma16010452 - 3 Jan 2023

Cited by 5 | Viewed by 2129

Abstract

Under corrosive environments, concrete material properties can deteriorate significantly, which can seriously affect structural safety. Therefore, it has important engineering applications to improve the durability performance at a lower economic cost. This paper proposes a new, highly durable concrete using inexpensive construction materials [...] Read more.

Under corrosive environments, concrete material properties can deteriorate significantly, which can seriously affect structural safety. Therefore, it has important engineering applications to improve the durability performance at a lower economic cost. This paper proposes a new, highly durable concrete using inexpensive construction materials such as basalt fiber, sodium methyl silicate, and inorganic aluminum salt waterproofing agent. With the massive application of sewage treatment projects, the problem of concrete durability degradation is becoming more and more serious. In this paper, five types of concrete are developed for the sewage environment, and the apparent morphology and fine structure of the specimens after corrosion in sewage were analyzed. The density, water absorption, and compressive strength were measured to investigate the deterioration pattern of concrete properties. It was found that ordinary concrete was subject to significant corrosion, generating large deposits of algae on the surface and accompanied by sanding. The new concrete showed superior corrosion resistance compared to conventional concrete. Among other factors, the inorganic aluminum salt waterproofing agent effect was the most prominent. The study found that the strength of ordinary concrete decreased by about 15% in the test environment, while the new concrete had a slight increase. Comprehensive evaluation showed that the combination of basalt fiber and inorganic aluminum salt waterproofing agent had the best effect. Its use is recommended. Full article

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12 pages, 5075 KiB

Open AccessArticle

Optimization of Single-Point Incremental Forming of Polymer Sheets through FEM

by Antonio Formisano, Luca Boccarusso and Massimo Durante

Materials 2023, 16(1), 451; https://doi.org/10.3390/ma16010451 - 3 Jan 2023

Cited by 11 | Viewed by 3060

Abstract

Incremental sheet forming represents a relatively new process appointed to form sheets of pure metals, alloys, polymers, and composites for the manufacture of components in fields where customized production in a short time and at a low cost is required. Its most common [...] Read more.

Incremental sheet forming represents a relatively new process appointed to form sheets of pure metals, alloys, polymers, and composites for the manufacture of components in fields where customized production in a short time and at a low cost is required. Its most common variant, named single-point incremental forming, is a flexible process using very simple tooling; the sheet is clamped along the edges and a hemispherical-headed tool follows a required path, to deform the sheet locally. In so doing, better formability is reached without any dedicated dies and for low-forming forces, which represent some of the attractive features of this process. Nevertheless, and with special reference to thermoplastic sheets, incremental formed parts suffer from peculiar defects like twisting and wrinkling. In this numerical work, analyses were conducted through a commercial finite element code by varying the toolpath strategy of the incremental forming of polycarbonate sheets. The investigation of some features like the forming forces, the deformation states, the energy levels, and the forming time was carried out, to determine the toolpath strategy able to optimize the incremental forming process of polymer sheets. The results of the numerical analyses highlight a reduction of the forming forces when using toolpaths alternating diagonal up and vertical down steps and, presumably, a reduced risk of failures and defects. Furthermore, these toolpath strategies solutions also have a positive impact on the environment in terms of energy and do not significantly increase the manufacturing time. Full article

(This article belongs to the Special Issue Advanced Incremental Sheet Forming of Hard-to-Work Materials)

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15 pages, 3226 KiB

Open AccessArticle

Fast-Setting Calcium Silicate-Based Pulp Capping Cements—Integrated Antibacterial, Irritation and Cytocompatibility Assessment

by Gabriel Kato, Pedro Sousa Gomes, Karin Hermana Neppelenbroek, Cláudia Rodrigues, Maria Helena Fernandes and Liliana Grenho

Materials 2023, 16(1), 450; https://doi.org/10.3390/ma16010450 - 3 Jan 2023

Cited by 6 | Viewed by 3291

Abstract

Calcium silicate-based cements (CSCs) are endodontic materials widely used in vital pulp-capping approaches. Concerning the clinical application, the reduced set time and pre-mixed formulations are relevant characteristics during the operative management of pulpal exposure, aiming to optimise the work time and improve cross-infection/asepsis [...] Read more.

Calcium silicate-based cements (CSCs) are endodontic materials widely used in vital pulp-capping approaches. Concerning the clinical application, the reduced set time and pre-mixed formulations are relevant characteristics during the operative management of pulpal exposure, aiming to optimise the work time and improve cross-infection/asepsis control. Additionally, clinical success seems to be greatly dependent on the biological performance of the materials that directly contact the living pulp. As such, this work approaches an integrative biological characterisation (i.e., antibacterial, irritation, and cytocompatibility assays) of three fast-setting CSCs—Biodentine^TM, TotalFill^® BC RRM™ Fast Putty, and Theracal LC^®. These cements, after setting for 24 h, presented the expected topography and elemental composition (assessed by scanning electron microscopy, coupled with EDS analysis), in accordance with the information of the manufacturer. The set cements displayed a significant and similar antibiofilm activity against S. mutans, in a direct contact assay. Twenty-four-hour eluates were not irritant in the standardised CAM assay, but elicited distinct dose- and time-dependent cytotoxicity profiles on fibroblastic cells—i.e., Biodentine was devoid of toxicity, TotalFill presented a slight dose-dependent initial toxicity that was easily overcome, and Theracal LC was deleterious at high concentrations. When compared to long-setting ProRoot MTA cement, which highlighted the pursued integrative approach, Biodentine presented a similar profile, but TotalFill and Theracal LC displayed a poorer performance regarding antibiofilm activity/cytocompatibility features, and Theracal LC suggested eventual safety concerns. Full article

(This article belongs to the Special Issue Advance in Biomaterials for Tissue Engineering)

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17 pages, 9893 KiB

Open AccessArticle

Correlations between Microstructure and Residual Stress of Nanoscale Depth Profiles for TSV-Cu/TiW/SiO₂/Si Interfaces after Different Thermal Loading

by Min Zhang, Fangzhou Chen, Fei Qin, Si Chen and Yanwei Dai

Materials 2023, 16(1), 449; https://doi.org/10.3390/ma16010449 - 3 Jan 2023

Cited by 5 | Viewed by 2434

Abstract

In this paper, the residual stresses with a nanoscale depth resolution at TSV-Cu/TiW/SiO₂/Si interfaces under different thermal loadings are characterized using the ion-beam layer removal (ILR) method. Moreover, the correlations of residual stress, microstructure, and the failure modes of the interfaces [...] Read more.

In this paper, the residual stresses with a nanoscale depth resolution at TSV-Cu/TiW/SiO₂/Si interfaces under different thermal loadings are characterized using the ion-beam layer removal (ILR) method. Moreover, the correlations of residual stress, microstructure, and the failure modes of the interfaces are discussed. The residual stresses at the interfaces of TSV-Cu/TiW, TiW/SiO₂, and SiO₂/Si are in the form of small compressive stress at room temperature, then turn into high-tensile stress after thermal cycling or annealing. In addition, the maximum residual stress inside the TSV-Cu is 478.54 MPa at room temperature, then decreases to 216.75 MPa and 90.45 MPa, respectively, after thermal cycling and annealing. The microstructural analysis indicates that thermal cycling causes an increase in the dislocation density and a decrease in the grain diameter of TSV-Cu. Thus, residual stress accumulates constantly in the TSV-Cu/TiW interface, resulting in the cracking of the interface. Furthermore, annealing leads to the cracking of more interfaces, relieving the residual stress as well as increasing the grain diameter of TSV-Cu. Besides this, the applicability of the ILR method is verified by finite element modeling (FEM). The influence of the geometric errors of the micro-cantilever beam and the damage to the materials introduced by the focused ion beam (FIB) in the experimental results are discussed. Full article

(This article belongs to the Topic Advances in Microelectronics and Semiconductor Engineering)

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19 pages, 3565 KiB

Open AccessArticle

Synthesis and Structure–Activity Relationship of 2,6-Disubstituted Thiosemicarbazone Derivatives of Pyridine as Potential Antituberculosis Agents

by Dagmara Ziembicka, Katarzyna Gobis, Małgorzata Szczesio, Andrzej Olczak, Ewa Augustynowicz-Kopeć, Agnieszka Głogowska, Izabela Korona-Głowniak and Krzysztof Bojanowski

Materials 2023, 16(1), 448; https://doi.org/10.3390/ma16010448 - 3 Jan 2023

Cited by 7 | Viewed by 2096

Abstract

In this study, six new 2,6-disubstituted thiosemicarbazone derivatives of pyridine were synthesized (4–9), and their tuberculostatic activity was evaluated. All of them showed two- to eightfold higher activity (minimum inhibitory concentration (MIC) 0.5–4 µg/mL) against the resistant strain compared [...] Read more.

In this study, six new 2,6-disubstituted thiosemicarbazone derivatives of pyridine were synthesized (4–9), and their tuberculostatic activity was evaluated. All of them showed two- to eightfold higher activity (minimum inhibitory concentration (MIC) 0.5–4 µg/mL) against the resistant strain compared with the reference drug. Compounds 5 and 7, which contained the most basic substituents—pyrrolidine and piperidine—in their structure, strongly inhibited the growth of the standard strain (MIC 2 µg/mL). Furthermore, the same derivatives exhibited activity comparable to that of the reference drugs against some types of Gram-positive bacteria (MIC 0.49 µg/mL) and showed no cytotoxicity (IC50 > 50 µg/mL) in HaCaT cells. The zwitterionic structure of each compound was determined using X-ray crystallography. Absorption, distribution, metabolism, and excretion analyses showed that all compounds are good drug candidates. Thus, compounds 5 and 7 were identified as leading structures for further research on antituberculosis drugs with extended effects. Full article

(This article belongs to the Special Issue Organic Compounds and Nanoparticles Studies for Applications in Cancer and Tuberculosis Therapeutics)

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22 pages, 6736 KiB

Open AccessArticle

Hybrid Data-Driven Deep Learning Framework for Material Mechanical Properties Prediction with the Focus on Dual-Phase Steel Microstructures

by Ali Cheloee Darabi, Shima Rastgordani, Mohammadreza Khoshbin, Vinzenz Guski and Siegfried Schmauder

Materials 2023, 16(1), 447; https://doi.org/10.3390/ma16010447 - 3 Jan 2023

Cited by 5 | Viewed by 3327

Abstract

A comprehensive approach to understand the mechanical behavior of materials involves costly and time-consuming experiments. Recent advances in machine learning and in the field of computational material science could significantly reduce the need for experiments by enabling the prediction of a material’s mechanical [...] Read more.

A comprehensive approach to understand the mechanical behavior of materials involves costly and time-consuming experiments. Recent advances in machine learning and in the field of computational material science could significantly reduce the need for experiments by enabling the prediction of a material’s mechanical behavior. In this paper, a reliable data pipeline consisting of experimentally validated phase field simulations and finite element analysis was created to generate a dataset of dual-phase steel microstructures and mechanical behaviors under different heat treatment conditions. Afterwards, a deep learning-based method was presented, which was the hybridization of two well-known transfer-learning approaches, ResNet50 and VGG16. Hyper parameter optimization (HPO) and fine-tuning were also implemented to train and boost both methods for the hybrid network. By fusing the hybrid model and the feature extractor, the dual-phase steels’ yield stress, ultimate stress, and fracture strain under new treatment conditions were predicted with an error of less than 1%. Full article

(This article belongs to the Special Issue Behavior of Metallic and Composite Structures (Third Volume))

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11 pages, 5594 KiB

Open AccessArticle

A Comparison of Low-Temperature Deformation Behavior and Fracture in Low-Carbon Steel Specimens Obtained by Electron Beam Additive Manufacturing and Conventional Casting and Normalization

by Elena Astafurova, Kseniya Reunova, Evgenii Melnikov, Marina Panchenko, Sergey Astafurov, Andrey Luchin, Elena Zagibalova and Evgenii Kolubaev

Materials 2023, 16(1), 446; https://doi.org/10.3390/ma16010446 - 3 Jan 2023

Cited by 1 | Viewed by 1625

Abstract

In the present work, the microstructure, phase composition, and temperature dependence of the mechanical properties and fracture micromechanisms of low-carbon steel produced by conventional casting and electron beam additive manufacturing have been studied. Regardless of the manufacturing method, the phase composition of steel [...] Read more.

In the present work, the microstructure, phase composition, and temperature dependence of the mechanical properties and fracture micromechanisms of low-carbon steel produced by conventional casting and electron beam additive manufacturing have been studied. Regardless of the manufacturing method, the phase composition of steel consists of ferrite with an insignificant fraction of carbides (pearlite grains in both types of steel and single coarse precipitates in the additively fabricated one). It was shown that the studied steels are characterized by a strong temperature dependence on yield strength and ultimate tensile strength. At T = 77 K, both types of steel are characterized by high strength properties, which decrease with increasing test temperatures up to 300 K. In addition, all deformation curves are characterized by the presence of a yield drop and yield plateau over the entire temperature range under study (77 K–300 K). A decrease in test temperature from 300 K to 77 K leads to a change in the fracture micromechanism of the steels from a dimple fracture to a cleavage one. Despite the similar deformation behavior and strength properties, the additively fabricated steel possesses lower elongation to failure at 77 K due to an insignificant fraction of coarse precipitates, which assists the nucleation of brittle cracks. Full article

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18 pages, 13690 KiB

Open AccessArticle

Microstructure Evolution, Constitutive Modelling, and Superplastic Forming of Experimental 6XXX-Type Alloys Processed with Different Thermomechanical Treatments

by Andrey G. Mochugovskiy, Ahmed O. Mosleh, Anton D. Kotov, Andrey V. Khokhlov, Ludmila Yu. Kaplanskaya and Anastasia V. Mikhaylovskaya

Materials 2023, 16(1), 445; https://doi.org/10.3390/ma16010445 - 3 Jan 2023

Cited by 14 | Viewed by 2303

Abstract

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the [...] Read more.

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the secondary particle distribution and deformation behavior was studied. The increase in hot rolling degree increased the homogeneity of the particle distribution in the aluminum-based solid solution that improved superplastic properties, providing an elongation of ~470–500% at increased strain rates of (0.5–1) × 10⁻² s⁻¹. A constitutive model based on Arrhenius and Beckofen equations was used to describe and predict the superplastic flow behavior of the alloy studied. Model complex-shaped parts were processed by superplastic forming at two strain rates. The proposed strain rate of 1 × 10⁻² s⁻¹ provided a low thickness variation and a high quality of the experimental parts. The residual cavitation after superplastic forming was also large at the low strain rate of 2 × 10⁻³ s⁻¹ and significantly smaller at 1 × 10⁻² s⁻¹. Coarse Al₉FeNi particles did not stimulate the cavitation process and were effective to provide the superplasticity of alloys studied at high strain rates, whereas cavities were predominately observed near coarse Mg₂Si particles, which act as nucleation places for cavities during superplastic deformation and forming. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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20 pages, 4964 KiB

Open AccessEditor’s ChoiceReview

A Review of Cu–Ni–Sn Alloys: Processing, Microstructure, Properties, and Developing Trends

by Lang Guo, Pengcheng Zuo, Zequn Zhang, Qianwen Zhang, Mengya Zhao, Xinyu Hou, Junsheng Wu and Bowei Zhang

Materials 2023, 16(1), 444; https://doi.org/10.3390/ma16010444 - 3 Jan 2023

Cited by 13 | Viewed by 4347

Abstract

Cu–Ni–Sn alloys have been widely used in the aerospace industry, the electronics industry, and other fields due to their excellent electrical and thermal conductivity, high strength, corrosion and wear resistance, etc., which make Cu–15Ni–8Sn alloys the perfect alternative to Cu–Be alloys. This paper [...] Read more.

Cu–Ni–Sn alloys have been widely used in the aerospace industry, the electronics industry, and other fields due to their excellent electrical and thermal conductivity, high strength, corrosion and wear resistance, etc., which make Cu–15Ni–8Sn alloys the perfect alternative to Cu–Be alloys. This paper begins with how Cu–Ni–Sn alloys are prepared. Then, the microstructural features, especially the precipitation order of each phase, are described. In addition, the influence of alloying elements, such as Si, Ti, and Nb, on its microstructure and properties is discussed. Finally, the effects of plastic deformation and heat treatment on Cu–Ni–Sn alloys are discussed. This review is able to provide insight into the development of novel Cu–Ni–Sn alloys with a high performance. Full article

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

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24 pages, 13135 KiB

Open AccessArticle

Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation

by Xiaoyu Zhao, Yuan Wei, Rami Mansour, Sasan Dadbakhsh and Amir Rashid

Materials 2023, 16(1), 443; https://doi.org/10.3390/ma16010443 - 3 Jan 2023

Cited by 3 | Viewed by 2133

Abstract

This paper develops a hybrid experimental/simulation method for the first time to assess the thermal stresses generated during electron beam melting (EBM) at high temperatures. The bending and rupture of trusses supporting Inconel 625 alloy panels at ~1050 °C are experimentally measured for [...] Read more.

This paper develops a hybrid experimental/simulation method for the first time to assess the thermal stresses generated during electron beam melting (EBM) at high temperatures. The bending and rupture of trusses supporting Inconel 625 alloy panels at ~1050 °C are experimentally measured for various scanning strategies. The generated thermal stresses and strains are thereafter simulated using the Finite-Element Method (FEM). It is shown that the thermal stresses on the trusses may reach the material UTS without causing failure. Failure is only reached after the part experiences a certain magnitude of plastic strain (~0.33 ± 0.01 here). As the most influential factor, the plastic strain increases with the scanning length. In addition, it is shown that continuous scanning is necessary since the interrupted chessboard strategy induces cracking at the overlapping regions. Therefore, the associated thermal deformation is to be minimized using a proper layer rotation according to the part length. Although this is similar to the literature reported for selective laser melting (SLM), the effect of scanning pattern is found to differ, as no significant difference in thermal stresses/strains is observed between bidirectional and unidirectional patterns from EBM. Full article

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

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17 pages, 8774 KiB

Open AccessArticle

Study of Transition Areas in Press-Hardened Steels in a Combined Tool for Hot and Cold Forming

by Filip Votava, Hana Jirková, Ludmila Kučerová and Štěpán Jeníček

Materials 2023, 16(1), 442; https://doi.org/10.3390/ma16010442 - 3 Jan 2023

Cited by 3 | Viewed by 2503

Abstract

Press-hardening, also known as hot stamping, is a manufacturing process for producing car body parts that must meet the high demands of their mechanical properties and safety parameters. Moreover, these components often require different mechanical properties in different parts of the component. This [...] Read more.

Press-hardening, also known as hot stamping, is a manufacturing process for producing car body parts that must meet the high demands of their mechanical properties and safety parameters. Moreover, these components often require different mechanical properties in different parts of the component. This work presents the press-hardening process in a special combined tool where one half of the tool is heated and the other half is cooled. The cooled part has been 3D printed due to the complexity of the internal cooling channels. The aim of this work is to investigate the variation of the microstructures in the sheet metal and the mechanical properties in relation to the cooling process in the tool and to determine the transition area where these properties cross over. Two steels were chosen for the experiment. The most commonly used steel 22MnB5, and an experimental high-strength steel with 0.2% C alloyed with manganese and aluminium. A temperature of 425 °C was set in the heated part of the tool, and different holding times in the tool were tested. In the heated part of the tool, a bainitic structure with a fraction of ferrite and retained austenite was formed, while in the quenched part of the tool, a martensitic transformation was promoted due to rapid cooling. In addition to microscopic analyses, mechanical tests and hardness measurements were also performed. Full article

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26 pages, 2506 KiB

Open AccessArticle

ACTAS: A New Framework for Mechanical and Frictional Characterization in Axisymmetric Compression Test

by Soheil Solhjoo

Materials 2023, 16(1), 441; https://doi.org/10.3390/ma16010441 - 3 Jan 2023

Cited by 3 | Viewed by 1903

Abstract

There are two common methods to interpret the results of an Axisymmetric Compression Test (ACT): the Cylindrical Profile Model (CPM) and the Avitzur model; however, both of the two and all other models available in the literature ignore the unavoidable foldover phenomenon, which [...] Read more.

There are two common methods to interpret the results of an Axisymmetric Compression Test (ACT): the Cylindrical Profile Model (CPM) and the Avitzur model; however, both of the two and all other models available in the literature ignore the unavoidable foldover phenomenon, which breaks the models to provide reliable friction-free flow stress curves. Here, a novel numerical framework (called ACTAS) is presented that incorporates the foldover. ACTAS can be used to both simulate and analyze ACT. Ten finite element models are used to benchmark ACTAS. The results show the reliability of the proposed method in estimating the average and pointwise stress-strain curves and friction factors. Moreover, a new solution is provided by coupling the CPM and the Avitzur model (called A-CPM), to obtain reliable average flow curves even after the onset of foldover. Full article

(This article belongs to the Section Mechanics of Materials)

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19 pages, 7374 KiB

Open AccessArticle

Large-Scale Model Test on Water Pressure Resistance of Lining Structure of Water-Rich Tunnel

by Mingli Huang, Meng Huang and Ze Yang

Materials 2023, 16(1), 440; https://doi.org/10.3390/ma16010440 - 3 Jan 2023

Cited by 1 | Viewed by 2149

Abstract

In order to solve the problem of testing the water pressure resistance of lining structures of water-rich tunnels and the difficulty of implementing the existing model tests, a large-scale model test method was proposed relying on the New Yuanliangshan Tunnel threatened by high [...] Read more.

In order to solve the problem of testing the water pressure resistance of lining structures of water-rich tunnels and the difficulty of implementing the existing model tests, a large-scale model test method was proposed relying on the New Yuanliangshan Tunnel threatened by high pressure and rich water. This method creatively transformed the external water pressure of the lining structure into internal water pressure, and the conversion coefficient of water resistance of lining under different sizes and loading modes was obtained by numerical calculation. Results showed that the ultimate water pressure resistance of the lining structure under an external uniformly distributed water pressure and local water pressure was 1.44 and 0.67 times of that obtained from the large-scale model tests, respectively. By conducting the large-scale model tests and combining with the conversion coefficient, the water pressure resistance of the actual tunnel lining could be obtained. Research indicated that water pressure resistance of K2.0 (bearing water pressure of 2.0 MPa) type lining at the transition section of karst caves and K3.0 (bearing water pressure of 3.0 MPa) type lining at the section of karst caves of the New Yuanliangshan Tunnel was 3.33 MPa and not less than 4.36 MPa, respectively, and the high reliability of the large-scale model tests was verified by numerical calculation, implying that the model test method could be extended to similar tunnel projects. Full article

(This article belongs to the Special Issue Novel Civil Engineering Materials Integrated with Structures)

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13 pages, 14655 KiB

Open AccessArticle

Effect of Zirconium Diboride and Titanium Diboride on the Structure and Properties of 316L Steel-Based Composites

by Iwona Sulima, Paweł Hyjek, Marcin Podsiadło and Sonia Boczkal

Materials 2023, 16(1), 439; https://doi.org/10.3390/ma16010439 - 3 Jan 2023

Cited by 1 | Viewed by 1814

Abstract

The effect of zirconium diboride (ZrB₂) and titanium diboride (TiB₂) on the microstructure as well as the physical, mechanical, and tribological properties of composites based on 316 L steel is presented. Each reinforcing phase was added to the base [...] Read more.

The effect of zirconium diboride (ZrB₂) and titanium diboride (TiB₂) on the microstructure as well as the physical, mechanical, and tribological properties of composites based on 316 L steel is presented. Each reinforcing phase was added to the base alloy in the amount of 5 wt% and 10 wt%. The composites were fabricated by the SPS process (Spark Plasma Sintering). The results show that the weight fraction of the reinforcing phase affects the physical, mechanical, and tribological properties of the sintered composites. The sintered materials were characterized by a very high level of density. The addition of TiB₂ has proved to be effective in increasing the hardness and compressive strength of the composites. The hardness of the composites with the addition of 10% TiB₂ increased by 100% compared to the hardness of sintered 316L steel. It was found that introducing ZrB₂ to the steel matrix significantly improved the wear resistance of the composites. The results showed that compared to 316L steel with the wear rate of 519 × 10⁻⁶ mm³/Nm, the wear rate of the composites containing 10% ZrB₂ decreased more than twice, i.e., to 243 × 10⁻⁶ mm³/Nm. Full article

(This article belongs to the Section Advanced Composites)

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11 pages, 3480 KiB

Open AccessArticle

Quasi-2D SnO₂ Thin Films for Gas Sensors: Chemoresistive Response and Temperature Effect on Adsorption of Analytes

by Alexander A. Petrunin and Olga E. Glukhova

Materials 2023, 16(1), 438; https://doi.org/10.3390/ma16010438 - 3 Jan 2023

Cited by 4 | Viewed by 1816

Abstract

We performed in silico calculations of electrical conductivity of quasi-2D SnO₂ thin films with a (110) surface–prospect material for sensitive element of gas sensors. Electronic structure, charge transfer and chemoresistive response of quasi-2D SnO₂ thin films during adsorption of alcohol molecules [...] Read more.

We performed in silico calculations of electrical conductivity of quasi-2D SnO₂ thin films with a (110) surface–prospect material for sensitive element of gas sensors. Electronic structure, charge transfer and chemoresistive response of quasi-2D SnO₂ thin films during adsorption of alcohol molecules (ethanol, methanol, isopropanol and butanol) and ketones (acetone, cyclopentanone and cyclohexanone) were calculated. It was found that the electrical conductivity of quasi-2D SnO₂ thin films decreases within 4–15% during adsorption of analytes. The influence of temperature on the concentration of analytes on the surface of quasi-2D SnO₂ thin films was explored in dependence analyte’s type. Full article

(This article belongs to the Special Issue Recent Progresses in Thermoelectric Materials)

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21 pages, 9022 KiB

Open AccessArticle

Near-Infrared (NIR) Silver Sulfide (Ag₂S) Semiconductor Photocatalyst Film for Degradation of Methylene Blue Solution

by Zahrah Ramadlan Mubarokah, Norsuria Mahmed, Mohd Natashah Norizan, Ili Salwani Mohamad, Mohd Mustafa Al Bakri Abdullah, Katarzyna Błoch, Marcin Nabiałek, Madalina Simona Baltatu, Andrei Victor Sandu and Petrica Vizureanu

Materials 2023, 16(1), 437; https://doi.org/10.3390/ma16010437 - 3 Jan 2023

Cited by 4 | Viewed by 2725

Abstract

A silver sulfide (Ag₂S) semiconductor photocatalyst film has been successfully synthesized using a solution casting method. To produce the photocatalyst films, two types of Ag₂S powder were used: a commercialized and synthesized powder. For the commercialized powder (CF/comAg₂ [...] Read more.

A silver sulfide (Ag₂S) semiconductor photocatalyst film has been successfully synthesized using a solution casting method. To produce the photocatalyst films, two types of Ag₂S powder were used: a commercialized and synthesized powder. For the commercialized powder (CF/comAg₂S), the Ag₂S underwent a rarefaction process to reduce its crystallite size from 52 nm to 10 nm, followed by incorporation into microcrystalline cellulose using a solution casting method under the presence of an alkaline/urea solution. A similar process was applied to the synthesized Ag₂S powder (CF/syntAg₂S), resulting from the co-precipitation process of silver nitrate (AgNO₃) and thiourea. The prepared photocatalyst films and their photocatalytic efficiency were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV-visible spectroscopy (UV-Vis). The results showed that the incorporation of the Ag₂S powder into the cellulose films could reduce the peak intensity of the oxygen-containing functional group, which indicated the formation of a composite film. The study of the crystal structure confirmed that all of the as-prepared samples featured a monoclinic acanthite Ag₂S structure with space group P₂₁/C. It was found that the degradation rate of the methylene blue dye reached 100% within 2 h under sunlight exposure when using CF/comAg₂S and 98.6% for the CF/syntAg₂S photocatalyst film, and only 48.1% for the bare Ag₂S powder. For the non-exposure sunlight samples, the degradation rate of only 33–35% indicated the importance of the semiconductor near-infrared (NIR) Ag₂S photocatalyst used. Full article

(This article belongs to the Special Issue Design and Applications of Functional Materials, Volume II)

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14 pages, 8536 KiB

Open AccessArticle

The Effect of B₄C Powder on Properties of the WAAM 2319 Al Alloy

by Xueping Song, Jinke Niu, Jiankang Huang, Ding Fan, Shurong Yu, Yuanjun Ma and Xiaoquan Yu

Materials 2023, 16(1), 436; https://doi.org/10.3390/ma16010436 - 3 Jan 2023

Cited by 7 | Viewed by 2292

Abstract

With ER2319 and B₄C powder as feedstocks and additives, respectively, a wire arc additive manufacturing (WAAM) system based on double-pulse melting electrode inert gas shielded welding (DP-MIG) was used to fabricate single-pass multilayer 2319 aluminum alloy. The results showed that, compared [...] Read more.

With ER2319 and B₄C powder as feedstocks and additives, respectively, a wire arc additive manufacturing (WAAM) system based on double-pulse melting electrode inert gas shielded welding (DP-MIG) was used to fabricate single-pass multilayer 2319 aluminum alloy. The results showed that, compared with additive manufacturing component without B₄C, the addition of which can effectively reduce the grain size (from 43 μm to 25 μm) of the tissue in the deposited layer area and improve its mechanical properties (from 231 MPa to 286 MPa). Meanwhile, the mechanical properties are better in the transverse than in the longitudinal direction. Moreover, the strengthening mechanism of B₄C on the mechanical properties of aluminum alloy additive manufacturing mainly includes dispersion strengthening from fine and uniform B₄C granular reinforcing phases and fine grain strengthening from the grain refinement of B₄C. These findings shed light on the B₄C induced grain refinement mechanism and improvement of WAAM 2319 Al alloy. Full article

(This article belongs to the Special Issue Additive Manufacturing (AM) of Metal Alloys: Microstructure and Mechanical Performance)

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19 pages, 13628 KiB

Open AccessArticle

Gas Atomization of Duplex Stainless Steel Powder for Laser Powder Bed Fusion

by Chengsong Cui, Felix Stern, Nils Ellendt, Volker Uhlenwinkel, Matthias Steinbacher, Jochen Tenkamp, Frank Walther and Rainer Fechte-Heinen

Materials 2023, 16(1), 435; https://doi.org/10.3390/ma16010435 - 3 Jan 2023

Cited by 7 | Viewed by 2544

Abstract

Duplex stainless steel powders for laser additive manufacturing have not been developed extensively. In this study, the melts of a super duplex stainless steel X2CrNiMoCuWN25-7-4 (AISI F55, 1.4501) were atomized with different process gases (Ar or N₂) at different atomization gas [...] Read more.

Duplex stainless steel powders for laser additive manufacturing have not been developed extensively. In this study, the melts of a super duplex stainless steel X2CrNiMoCuWN25-7-4 (AISI F55, 1.4501) were atomized with different process gases (Ar or N₂) at different atomization gas temperatures. The process gas N₂ in the melting chamber leads to a higher nitrogen dissolution in the steel and a higher nitrogen content of the atomized powders. The argon-atomized powders have more gas porosity inside the particles than the nitrogen-atomized powders. In addition, the higher the atomization gas temperature, the finer the powder particles. The duplex stainless steel powders showed good processability during PBF-LB/M (Laser powder bed fusion). The gas entrapment in the powder particles, regardless of the gas chemistry and the gas content, appears to have a negligible effect on the porosity of the as-built parts. Full article

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17 pages, 5144 KiB

Open AccessArticle

Design of Real-Time Extremum-Seeking Controller-Based Modelling for Optimizing MRR in Low Power EDM

by Mohamed Rabik Mohamed Ismail, Muthuramalingam Thangaraj, Panagiotis Karmiris-Obratański, Emmanouil Papazoglou and Nikolaos Karkalos

Materials 2023, 16(1), 434; https://doi.org/10.3390/ma16010434 - 3 Jan 2023

Cited by 10 | Viewed by 1759

Abstract

Electric discharge machining (EDM) is one of the non-conventional machining processes that supports machining for high-strength and wear-resistant materials. It is a challenging task to select the process parameters in real-time to maximize the material removal rate since real-time process trials are expensive [...] Read more.

Electric discharge machining (EDM) is one of the non-conventional machining processes that supports machining for high-strength and wear-resistant materials. It is a challenging task to select the process parameters in real-time to maximize the material removal rate since real-time process trials are expensive and the EDM process is stochastic. For the ease of finding process parameters, a modelling of the EDM process is proposed. Due to the non-linear relationship between the material removal rate (MRR) and discharge time, a model-free adaptive extremum-seeking controller (ESC) is proposed in the feedback path of the EDM process for finding an optimal value of the discharge time at which the maximum material removal rate can be achieved. The results of the model show a performance that is closer to the actual process by choosing steel workpieces and copper electrodes. The proposed model offers a lower error rate when compared with actual experimental process data. When compared to manual searching for an optimal point, extreme seeking online searching performed better as per the experimental results. It was observed that the experimental validation also proved that the ESC can produce a large MRR by tracking the extremum control. The present study has been limited to only the MRR, but it is also possible to implement such algorithms for more than one response parameter optimization in future studies. In such cases the performance measures of the process could be further enhanced, which could be used for a real-time complex die- and mold-making process using EDM. Full article

(This article belongs to the Special Issue Advanced Machining Technology for Modern Engineering Materials)

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