Materials

10 pages, 621 KiB

Open AccessSystematic Review

Treatment Prognosis of Restored Teeth with Crown Lengthening vs. Deep Margin Elevation: A Systematic Review

by Maryam H. Mugri, Mohammed E. Sayed, Binoy Mathews Nedumgottil, Shilpa Bhandi, A. Thirumal Raj, Luca Testarelli, Zohaib Khurshid, Saurabh Jain and Shankargouda Patil

Materials 2021, 14(21), 6733; https://doi.org/10.3390/ma14216733 - 08 Nov 2021

Cited by 14 | Viewed by 7943

Abstract

Crown lengthening surgery and deep margin elevation are two distinct approaches used to manage decayed teeth. This systematic review examined the survival rate of badly decayed teeth when restored using the crown lengthening technique and compared it to the deep margin elevation technique. [...] Read more.

Crown lengthening surgery and deep margin elevation are two distinct approaches used to manage decayed teeth. This systematic review examined the survival rate of badly decayed teeth when restored using the crown lengthening technique and compared it to the deep margin elevation technique. The search was conducted during July 2020 and then again updated at the end of July 2021, and no restriction concerning publication status and time was applied during the search. Cochrane Database, EBSCO, Scopus, and Medline databases were searched electronically for relevant literature. Google Scholar was used as a secondary source. Predefined inclusion and exclusion criteria were used to select the relevant articles. PRISMA guidelines were followed. The focused PICO question was: ‘Does the crown lengthening technique (I) provide a better survival rate (O) than deep margin elevation technique (C) following the restoration of badly decayed teeth (P).’ A total of six articles were included after performing screening based on the eligibility criteria. Four studies focused on crown lengthening while two focused on deep margin elevation technique. A majority of the studies showed a high risk of bias owing to methodological insufficiencies. Crown lengthening (CL) treated cases showed a change in the free gingival margin at six months post-surgery. A tissue rebound was seen that was correlated to the periodontal biotype. Teeth treated with the deep margin elevation (DME) technique showed high survivability. There is a lack of high-quality trials examining surgical comparisons between CL and DME with long-term follow-up. Patient- and dentist-reported outcomes have not been given adequate consideration in the literature. Based on the limited evidence, it can be concluded that for restorative purposes, crown lengthening surgery can be successful in long-term retention of restored teeth. However, the deep margin elevation technique has a better survival ratio. Future well-designed and executed research will have an effect on the evidence and level of certainty for the best approach to treating severely decayed teeth. Full article

(This article belongs to the Special Issue Bioinspired Materials for Dentistry)

► Show Figures

Figure 1

17 pages, 8363 KiB

Open AccessArticle

Microstructural and Mechanical Characterization of Additive Friction Stir-Deposition of Aluminum Alloy 5083 Effect of Lubrication on Material Anisotropy

by Brandon J. Phillips, C. Jacob Williamson, Ryan P. Kinser, J. Brian Jordon, Kevin J. Doherty and Paul G. Allison

Materials 2021, 14(21), 6732; https://doi.org/10.3390/ma14216732 - 08 Nov 2021

Cited by 22 | Viewed by 3059

Abstract

Additive Friction Stir-Deposition (AFS-D) is a transformative, metallic additive manufacturing (AM) process capable of producing near-net shape components with a wide variety of material systems. The solid-state nature of the process permits many of these materials to be successfully deposited without the deleterious [...] Read more.

Additive Friction Stir-Deposition (AFS-D) is a transformative, metallic additive manufacturing (AM) process capable of producing near-net shape components with a wide variety of material systems. The solid-state nature of the process permits many of these materials to be successfully deposited without the deleterious phase and thermally activated defects commonly observed in other metallic AM technologies. This work is the first to investigate the as-deposited microstructure and mechanical performance of a free-standing AA5083 deposition. An initial process parameterization was conducted to down-select optimal parameters for a large deposition to examine build direction properties. Microscopy revealed that constitutive particles were dispersed evenly throughout the matrix when compared to the rolled feedstock. Electron backscatter diffraction revealed a significant grain refinement from the inherent dynamic recrystallization from the AFS-D process. Tensile experiments determined a drop in yield strength, but an improvement in tensile strength in the longitudinal direction. However, a substantial reduction in tensile strength was observed in the build direction of the structure. Subsequent fractographic analysis revealed that the recommended lubrication applied to the feedstock rods, necessary for successful depositions via AFS-D, was ineffectively dispersed into the structure. As a result, lubrication contamination became entrapped at layer boundaries, preventing adequate bonding between layers. Full article

(This article belongs to the Topic Structure and Properties Modification in Additive Manufacturing)

► Show Figures

Figure 1

16 pages, 2549 KiB

Open AccessArticle

In Situ Control of Thermal Activation Conditions by Color for Serpentines with a High Iron Content

by Tatiana K. Ivanova, Irina P. Kremenetskaya, Andrey I. Novikov, Valentin G. Semenov, Anatoly G. Nikolaev and Marina V. Slukovskaya

Materials 2021, 14(21), 6731; https://doi.org/10.3390/ma14216731 - 08 Nov 2021

Cited by 2 | Viewed by 1803

Abstract

Serpentine heat treatment at temperatures of 650–750 °C yields magnesium–silicate reagent with high chemical activity. Precise and express control of roasting conditions in laboratory kilns and industrial aggregates is needed to derive thermally activated serpentines on a large scale. Color change in serpentines [...] Read more.

Serpentine heat treatment at temperatures of 650–750 °C yields magnesium–silicate reagent with high chemical activity. Precise and express control of roasting conditions in laboratory kilns and industrial aggregates is needed to derive thermally activated serpentines on a large scale. Color change in serpentines with a high iron content during roasting might be used to indicate the changes in chemical activity in the technological process. This study gives a scientific basis for the express control of roasting of such serpentines by comparing the colors of the obtained material and the reference sample. Serpentines with different chemical activity were studied by X-ray diffraction, Mössbauer spectroscopy, and optical spectroscopy. The color parameters were determined using RGB (red, green, blue), CIELAB (International Commission on Illumination 1976 L*a*b), and HSB (hue, brightness, saturation) color models. The color of heat-treated samples was found to be affected by changes in the crystallochemical characteristics of iron included in the structure of the serpentine minerals. The color characteristics given by the CIELAB model were in good coherence with the acid-neutralizing ability and optical spectra of heat-treated serpentines. Thus, in contrast to the long-term analysis by these methods, the control by color palette provides an express assessment of the quality of the resulting product. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Figure 1

17 pages, 4690 KiB

Open AccessArticle

Hydrogen Absorption and Desorption Behavior on Aluminum-Coated Hot-Stamped Boron Steel during Hot Press Forming and Automotive Manufacturing Processes

by Hye-Jin Kim, Hyun-Yeong Jung, Seung-Pill Jung, Ji-Hee Son, Joo-Sik Hyun and Ju-Sung Kim

Materials 2021, 14(21), 6730; https://doi.org/10.3390/ma14216730 - 08 Nov 2021

Cited by 3 | Viewed by 1863

Abstract

Our study mainly focused on diffusible hydrogen in aluminum–silicon-coated hot-stamped boron steel during a hot press forming process and in pre-treatment sequential lines of the automotive manufacturing process using a thermal desorption spectroscopy (TDS) technique. First, in the hot stamping procedure, as the [...] Read more.

Our study mainly focused on diffusible hydrogen in aluminum–silicon-coated hot-stamped boron steel during a hot press forming process and in pre-treatment sequential lines of the automotive manufacturing process using a thermal desorption spectroscopy (TDS) technique. First, in the hot stamping procedure, as the soaking time increased in the heating furnace at a specific dew point when austenitizing, a high concentration of diffusible hydrogen was absorbed into the hot-stamped boron steel. Based on the TDS analysis of hydrogen absorbed from hot stamping, the activation energy value of hydrogen trapping in 1.8 GPa grade steel is lower than that of 1.5 GPa grade steel. This means that diffusible hydrogen can be more easily diffused into defective sites of the microstructure at a higher level of the tensile strength grade. Second, in sequential pre-treatment lines of the automotive manufacturing process, additional hydrogen did not flow into the surface, and an electro-deposition process, including a baking procedure, was effective in removing diffusible hydrogen, which was similar to the residual hydrogen of the as-received state (i.e., initial cold rolled blank). Based on these results, the hydrogen absorption was facilitated during hot press forming, but the hydrogen was sequentially desorbed during automotive sequential lines on aluminum-coated hot-stamped steel parts. Full article

(This article belongs to the Special Issue Reliability of Structural Integrity and Engineering Materials)

► Show Figures

Figure 1

14 pages, 46759 KiB

Open AccessArticle

An Effective Expanded Graphite Coating on Polystyrene Bead for Improving Flame Retardancy

by Minjung Bae, Hyunhwa Lee, Gyeongseok Choi and Jaesik Kang

Materials 2021, 14(21), 6729; https://doi.org/10.3390/ma14216729 - 08 Nov 2021

Cited by 2 | Viewed by 2366

Abstract

Although foamed plastic insulation is widely used in construction in the Korean market, it is vulnerable to fire. To improve the flame retardancy, the method of flame-retardant coating with the EG in water-soluble state on the surface of expanded polystyrene (EPS) beads has [...] Read more.

Although foamed plastic insulation is widely used in construction in the Korean market, it is vulnerable to fire. To improve the flame retardancy, the method of flame-retardant coating with the EG in water-soluble state on the surface of expanded polystyrene (EPS) beads has been widely used. However, polystyrene beads coated with a water-soluble flame retardant easily separate the coated flame retardant in manufacturing. In this study is devised a flame-retardant coating and two steps of coating process for adhering the flame-retardant coating film evenly to the surface of the polystyrene bead without exfoliation. It was analyzed whether a flame-retardant EPS (FR-EPS) with excellent flame retardancy could be manufactured using polystyrene beads coated in this way. Ten FR-EPS samples satisfied the HF-1 and V-0 levels in horizontal and vertical burning tests, respectively. The THR of eight FR-EPS samples for ten minutes did not exceed 8 MJ∙m⁻² and the maximum HRR did not exceed 200 kW∙m⁻² for more than ten consecutive seconds. FR-EPS passed the building material standard of semi-nonflammability in Korean regulations, in contrast to commercial EPS, which have not passed the semi-nonflammability standard. It was also analyzed how effective the designed coating is in this study, comparing it with composites that were planned to improve the flame resistance of polystyrene, as reported in the literature. Flame Retardancy Index (FRI) values of FR-EPS proved the “excellent” level and had higher values compared with other polystyrene composites. These results demonstrated that the coated EPS containing a water-soluble flame retardant manufactured from EG and two steps of application with the coating solution achieved fire safety standard regulations. Full article

(This article belongs to the Special Issue Environmentally Friendly Materials in Construction)

► Show Figures

Figure 1

19 pages, 102049 KiB

Open AccessArticle

Analytical and Numerical Investigation of an Electrochemical Chloride Barrier for Reinforced Concrete Structures

by Carla Driessen-Ohlenforst and Michael Raupach

Materials 2021, 14(21), 6728; https://doi.org/10.3390/ma14216728 - 08 Nov 2021

Viewed by 1054

Abstract

During the development of a carbon-reinforced mortar interlayer for bridges, the idea of an electrochemical chloride barrier arose. An electrical field is generated between two carbon meshes, and the negatively charged chloride ions are held on the polarized upper carbon mesh to prevent [...] Read more.

During the development of a carbon-reinforced mortar interlayer for bridges, the idea of an electrochemical chloride barrier arose. An electrical field is generated between two carbon meshes, and the negatively charged chloride ions are held on the polarized upper carbon mesh to prevent chloride-induced corrosion in the reinforcement. Laboratory tests unexpectedly showed that higher voltages lead to an increase in chloride ions for certain depths of the reference probes. This paper discusses the implementation of analytical and numerical models that finally explain the effect only by the acting diffusion and migration with the help of a finite differences model and finite elements simulations. The effect of the local minimum is limited to positions above the depth of the first carbon layer of the test specimens. It is caused by the lines of the electrical field between the first and second carbon layer. According to the experimental and finite elements simulation results, higher voltages lead to lower chloride concentrations for all positions below the first carbon layer only after sufficient time duration. Therefore, the intended effect of an electrochemical chloride barrier can in general only be observed and confirmed after a certain time depending on position, conditions and parameters. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

► Show Figures

Figure 1

16 pages, 47452 KiB

Open AccessArticle

Effect of Indentation Load on Nanomechanical Properties Measured in a Multiphase Boride Layer

by Piotr Dziarski and Natalia Makuch

Materials 2021, 14(21), 6727; https://doi.org/10.3390/ma14216727 - 08 Nov 2021

Viewed by 1191

Abstract

The study investigated the dependence of the indentation load on nanomechanical properties for a gas-borided layer produced on Inconel 600-alloy. During the measurements, the indentation load range from 10 mN to 500 mN was used. Three types of tested areas, differing in the [...] Read more.

The study investigated the dependence of the indentation load on nanomechanical properties for a gas-borided layer produced on Inconel 600-alloy. During the measurements, the indentation load range from 10 mN to 500 mN was used. Three types of tested areas, differing in the concentration of chromium, were examined. The increase in chromium concentration was accompanied by an increase in indentation hardness and Young’s modulus. Simultaneously, the increase in the indentation load resulted in a decrease in the indentation hardness and Young’s modulus, for each type of the tested area. The presence of the indentation size effect was analyzed using four models: Meyer’s law, Hays and Kendall model, Li and Bradt model, Nix and Gao model. For all tested areas, good agreement with the Meyer’s law was obtained. However, areas with a higher chromium concentration were more susceptible to indentation size effect (ISE). The proportional specimen resistance (PSR) model was used to describe the plastic-elastic behavior of the tested materials, as well as to detect the presence of ISE. It was found that the increase in chromium concentration in the tested area was accompanied by a greater tendency to elastic deformation during nanoindentation. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

35 pages, 15952 KiB

Open AccessReview

Friction Stir Welding/Processing of Mg-Based Alloys: A Critical Review on Advancements and Challenges

by Farzad Badkoobeh, Hossein Mostaan, Mahdi Rafiei, Hamid Reza Bakhsheshi-Rad and Filippo Berto

Materials 2021, 14(21), 6726; https://doi.org/10.3390/ma14216726 - 08 Nov 2021

Cited by 28 | Viewed by 3363

Abstract

Friction stir welding (FSW) and friction stir processing (FSP) are two of the most widely used solid-state welding techniques for magnesium (Mg) and magnesium alloys. Mg-based alloys are widely used in the railway, aerospace, nuclear, and marine industries, among others. Their primary advantage [...] Read more.

Friction stir welding (FSW) and friction stir processing (FSP) are two of the most widely used solid-state welding techniques for magnesium (Mg) and magnesium alloys. Mg-based alloys are widely used in the railway, aerospace, nuclear, and marine industries, among others. Their primary advantage is their high strength-to-weight ratio and usefulness as a structural material. Due to their properties, it is difficult to weld using traditional gas- or electric-based processes; however, FSW and FSP work very well for Mg and its alloys. Recently, extensive studies have been carried out on FSW and FSP of Mg-based alloys. This paper reviews the context of future areas and existing constraints for FSW/FSP. In addition, in this review article, in connection with the FSW and FSP of Mg alloys, research advancement; the influencing parameters and their influence on weld characteristics; applications; and evolution related to the microstructure, substructure, texture and phase formations as well as mechanical properties were considered. The mechanisms underlying the joining and grain refinement during FSW/FSP of Mg alloys-based alloys are discussed. Moreover, this review paper can provide valuable and vital information regarding the FSW and FSP of these alloys for different sectors of relevant industries. Full article

(This article belongs to the Special Issue An Overview of Recent Materials for Targeted Applications)

► Show Figures

Figure 1

12 pages, 3078 KiB

Open AccessArticle

Preliminary Process and Microstructure Examination of Flux-Cored Wire Arc Additive Manufactured 18Ni-12Co-4Mo-Ti Maraging Steel

by Krzysztof Pańcikiewicz

Materials 2021, 14(21), 6725; https://doi.org/10.3390/ma14216725 - 08 Nov 2021

Cited by 5 | Viewed by 1600

Abstract

The production of large-size elements using additive manufacturing is a constantly evolving field that includes technological and material solutions. There is a need for a detailed analysis of the process and the products thus manufactured. In line with this trend, the flux-cored wire [...] Read more.

The production of large-size elements using additive manufacturing is a constantly evolving field that includes technological and material solutions. There is a need for a detailed analysis of the process and the products thus manufactured. In line with this trend, the flux-cored wire arc additive manufactured process and the part made of 18Ni-12Co-4Mo-Ti maraging steel were examined. The interpass temperature below 150 °C, the variation of the starting point and the gas flow of 12 L/min with a pre-flow of 2 s ensure the correct shape of the layers. The manufactured part underwent chemical composition analysis, macro- and microscopic examination and hardness measurements; in addition thermodynamic calculations were performed. The part is divided into a light-etched area (bottom part of the sample) with a hardness of 375 ± 12 HV10 and a dark-etched area (top part of the sample) with a hardness of 525 ± 11 HV10. Microscopic observations in the last layers showed supersaturated martensite with primary precipitates of μ-phase intermetallic compounds in intercellular spaces. In the earlier layers aging martensite with austenite and primary precipitates of intermetallic compounds were revealed. The share of austenite was 11.435 ± 1.313%. Full article

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

► Show Figures

Figure 1

16 pages, 5195 KiB

Open AccessArticle

Supervised Learning for Predictive Pore Size Classification of Regenerated Cellulose Membranes Based on Atomic Force Microscopy Measurements

by Alex Hadsell, Huong Chau, Richard Barber, Jr., Unyoung Kim and Maryam Mobed-Miremadi

Materials 2021, 14(21), 6724; https://doi.org/10.3390/ma14216724 - 08 Nov 2021

Cited by 1 | Viewed by 1868

Abstract

Nanoporous dialysis membranes made of regenerated cellulose are used as molecular weight cutoff standards in bioseparations. In this study, mesoporous standards with Stokes’ radii (50 kDa/2.7 nm, 100 kDa/3.4 nm and 1000 kDa/7.3 nm) and overlapping skewed distributions were characterized using AFM, with [...] Read more.

Nanoporous dialysis membranes made of regenerated cellulose are used as molecular weight cutoff standards in bioseparations. In this study, mesoporous standards with Stokes’ radii (50 kDa/2.7 nm, 100 kDa/3.4 nm and 1000 kDa/7.3 nm) and overlapping skewed distributions were characterized using AFM, with the specific aim of generating pore size classifiers for biomimetic membranes using supervised learning. Gamma transformation was used prior to conducting discriminant analysis in terms of the area under the receiver operating curve (AUC) and classification accuracy (Acc). Monte Carlo simulations were run to generate datasets (n = 10) on which logistic regression was conducted using a constant ratio of 80:20 (measurement:algorithm training), followed by algorithm validation by WEKA. The proposed algorithm can classify the 1000 kDa vs. 100 kDa (AUC > 0.8) correctly, but discrimination is weak for the 100 kDa vs. 50 kDa (AUC < 0.7), the latter being attributed to the instrument accuracy errors below 5 nm. As indicated by the results of the cross-validation study, a test size equivalent to 70% (AUC_tapping = 0.8341 ± 0.0519, Acc_tapping = 76.8% ± 5.9%) and 80% (AUC_fluid = 0.7614 ± 0.0314, Acc_tfluid = 76.2% ± 1.0%) of the training sets for the tapping and fluid modes are needed for correct classification, resulting in predicted reduction of scan times. Full article

(This article belongs to the Special Issue Application of Scanning Probe Techniques in the Study of Biomaterials and Biomechanisms)

► Show Figures

Graphical abstract

13 pages, 3908 KiB

Open AccessArticle

Rational Design and Characterization of Symmetry-Breaking Organic Semiconductors in Polymer Solar Cells: A Theory Insight of the Asymmetric Advantage

by Zezhou Liang, Lihe Yan, Jinhai Si, Pingping Gong, Xiaoming Li, Deyu Liu, Jianfeng Li and Xun Hou

Materials 2021, 14(21), 6723; https://doi.org/10.3390/ma14216723 - 08 Nov 2021

Cited by 23 | Viewed by 1952

Abstract

Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unit_A)—n1, n2, and n3—and three electron-donating units (unit [...] Read more.

Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unit_A)—n1, n2, and n3—and three electron-donating units (unit_D)—D, E, and F—with their π-conjugation area extended. The relationships between symmetric/asymmetric molecule structure and the performance of the oligomers are investigated using the density functional theory (DFT) and time-dependent density functional theory (TD–DFT) calculations. The results indicate that asymmetry molecule PEn2 has the minimum dihedral angle in the angle between two planes of unit_D and unit_A among all the molecules, which exhibited the advantages of asymmetric structures in molecular stacking. The relationship of the values of ionization potentials (IP) and electron affinities (EA) along with the unit_D/unit_A π-extend are revealed. The calculated reorganization energy results also demonstrate that the asymmetric molecules PDn2 and PEn2 could better charge the extraction of the PSCs than other molecules for their lower reorganization energy of 0.180 eV and 0.181 eV, respectively. Full article

(This article belongs to the Topic First-Principles Simulation—Nano-Theory)

► Show Figures

Graphical abstract

24 pages, 10601 KiB

Open AccessArticle

Structural Response of Bonded Joints between FRP Composite Strips and Steel Plates

by Vlad Lupășteanu, Dragoș Ungureanu, Nicolae Țăranu, Dorina Nicolina Isopescu, Radu Lupășteanu and Petru Mihai

Materials 2021, 14(21), 6722; https://doi.org/10.3390/ma14216722 - 08 Nov 2021

Cited by 4 | Viewed by 1407

Abstract

This paper presents the outcomes of an experimental and numerical study performed on epoxy-bonded single lap joints (SLJs) between carbon fiber-reinforced polymer (CFRP) composite strips and steel elements. For the experimental program, 34 specimens were prepared by varying the type of the composite [...] Read more.

This paper presents the outcomes of an experimental and numerical study performed on epoxy-bonded single lap joints (SLJs) between carbon fiber-reinforced polymer (CFRP) composite strips and steel elements. For the experimental program, 34 specimens were prepared by varying the type of the composite strip and the type of adhesives and their thicknesses; all specimens were loaded in axial tension up to failure. The specific failure mechanisms were identified and commented on the basis of the performed tests, and the load–displacement curves were plotted. Additionally, the strain distributions along the bond lengths at different load stages, the shear stress–displacements (slip) variations and the stress–strain distributions for the CFRP strips were plotted and investigated. The numerical simulations, based on 3D finite element method (FEM) analysis, provided consistent results, in good agreement with the experimental ones for all parameters that were investigated and discussed in this paper. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

► Show Figures

Figure 1

14 pages, 35889 KiB

Open AccessArticle

Influence of CNT Incorporation on the Carbonation of Conductive Cement Mortar

by Gun-Cheol Lee, Youngmin Kim, Soo-Yeon Seo, Hyun-Do Yun and Seongwon Hong

Materials 2021, 14(21), 6721; https://doi.org/10.3390/ma14216721 - 08 Nov 2021

Cited by 2 | Viewed by 1335

Abstract

This study analyzed the influence of carbon nanotubes (CNTs) on the carbonation conductive cementitious composites. Two powder types of CNT, multi-walled and single-wall CNTs, were employed to give the cement mortar the conductivity, and four tests including the accelerated carbonation, compressive and flexural [...] Read more.

This study analyzed the influence of carbon nanotubes (CNTs) on the carbonation conductive cementitious composites. Two powder types of CNT, multi-walled and single-wall CNTs, were employed to give the cement mortar the conductivity, and four tests including the accelerated carbonation, compressive and flexural strength, electrical resistance, and porosity tests were carried out. To intentionally accelerate the carbonation, the prismatic specimens of conductive cement composites were fabricated and stored in the controlled environmental chamber at a constant temperature of 20 ± 2 °C, constant relative humidity of 60 ± 5%, and carbon dioxide (CO₂) concentration of 5% for 12 weeks. It was observed that carbonation resulted in only chemical damage so that there was no change in the electrical resistance value of conductive cementitious mortar that had undergone a carbonation attack. Full article

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

► Show Figures

Figure 1

17 pages, 3958 KiB

Open AccessFeature PaperArticle

3D Printing in Alginic Acid Bath of In-Situ Crosslinked Collagen Composite Scaffolds

by Priscila Melo, Giorgia Montalbano, Sonia Fiorilli and Chiara Vitale-Brovarone

Materials 2021, 14(21), 6720; https://doi.org/10.3390/ma14216720 - 08 Nov 2021

Cited by 5 | Viewed by 2497

Abstract

Bone-tissue regeneration is a growing field, where nanostructured-bioactive materials are designed to replicate the natural properties of the target tissue, and then are processed with technologies such as 3D printing, into constructs that mimic its natural architecture. Type I bovine collagen formulations, containing [...] Read more.

Bone-tissue regeneration is a growing field, where nanostructured-bioactive materials are designed to replicate the natural properties of the target tissue, and then are processed with technologies such as 3D printing, into constructs that mimic its natural architecture. Type I bovine collagen formulations, containing functional nanoparticles (enriched with therapeutic ions or biomolecules) or nanohydroxyapatite, are considered highly promising, and can be printed using support baths. These baths ensure an accurate deposition of the material, nonetheless their full removal post-printing can be difficult, in addition to undesired reactions with the crosslinking agents often used to improve the final structural integrity of the scaffolds. Such issues lead to partial collapse of the printed constructs and loss of geometrical definition. To overcome these limitations, this work presents a new alternative approach, which consists of adding a suitable concentration of crosslinking agent to the printing formulations to promote the in-situ crosslinking of the constructs prior to the removal of the support bath. To this aim, genipin, chosen as crosslinking agent, was added (0.1 wt.%) to collagen-based biomaterial inks (containing either 38 wt.% mesoporous bioactive glasses or 65 wt.% nanohydroxyapatite), to trigger the crosslinking of collagen and improve the stability of the 3D printed scaffolds in the post-processing step. Moreover, to support the material deposition, a 15 wt.% alginic acid solution was used as a bath, which proved to sustain the printed structures and was also easily removable, allowing for the stable processing of high-resolution geometries. Full article

(This article belongs to the Special Issue Biodegradable and Biocompatible Polymer-Based Materials for Biomedical Engineering)

► Show Figures

Graphical abstract

13 pages, 11127 KiB

Open AccessArticle

Cherenkov Radiation Detection on a LS Counter for ²²⁶Ra Determination in Water and Its Comparison with Other Common Methods

by Ivana Stojković, Nataša Todorović, Jovana Nikolov, Branka Radulović and Michele Guida

Materials 2021, 14(21), 6719; https://doi.org/10.3390/ma14216719 - 08 Nov 2021

Viewed by 1512

Abstract

Reliable determination of ²²⁶Ra content in drinking water, surface water and groundwater is required for radiological health-risk assessment of populations and radiation-dose calculations after ingestion and inhalation. This study aimed to determine ²²⁶Ra presence in the untreated water samples on a [...] Read more.

Reliable determination of ²²⁶Ra content in drinking water, surface water and groundwater is required for radiological health-risk assessment of populations and radiation-dose calculations after ingestion and inhalation. This study aimed to determine ²²⁶Ra presence in the untreated water samples on a liquid scintillation counter via Cherenkov radiation detection. Cherenkov counting is a faster, simpler, less expensive technique than other commonly used methods for ²²⁶Ra determination. Step-by-step optimization of this technique on the Quantulus detector is presented in this paper. Improvement of detection limit/efficiency in the presence of sodium salicylate was investigated in this study. The main parameters of the method obtained were detection efficiency 15.87 (24)% and detection limit 0.415 Bq/L achieved for 1000 min of counting in 20 mL of sample volume. When 1 g of sodium salicylate was added, efficiency increased to 38.1 (5)%, with a reduction in the detection limit to 0.248 Bq/L for 500 min of counting. A satisfactory precision level of Cherenkov counting was obtained, the results deviating between 5% and 20% from reference values. The precision and accuracy of the Cherenkov counting technique were compared to liquid scintillation counting (EPA Method 913.0 for radon determination) and gamma spectrometry (the direct method for the untreated water samples on HPGe spectrometer). An overview of the advantages/disadvantages of each technique is elaborated in this paper. Full article

(This article belongs to the Special Issue Detectors for Assessment of Natural Radioactivity in Drinking Water: Materials and Method)

► Show Figures

Figure 1

11 pages, 1615 KiB

Open AccessArticle

Influence of Nanoscale Inhomogeneity Incorporating Interface Effect on Crack Nucleation at Intersection of Twin and Grain Boundary in Nanocomposite

by Yongshu Tao, Liang Li, Guanghong Miao and Jilei Dong

Materials 2021, 14(21), 6718; https://doi.org/10.3390/ma14216718 - 08 Nov 2021

Viewed by 1318

Abstract

Nanocracks can generate at the intersection of the deformation twin and grain boundary (GB). A mathematical model is built to study the nanoinhomogeneity effect on nanocrack nucleation and propagation in the nanocrystalline matrix. The boundary condition at the interface between the nanoinhomogeneity and [...] Read more.

Nanocracks can generate at the intersection of the deformation twin and grain boundary (GB). A mathematical model is built to study the nanoinhomogeneity effect on nanocrack nucleation and propagation in the nanocrystalline matrix. The boundary condition at the interface between the nanoinhomogeneity and the matrix is modified by incorporating the interface effect. The influence of the nanoinhomogeneity shear modulus, the nanoinhomogeneity radius, the nanoinhomogeneity position, the interface effect, and the external stress on the nanocrack nucleation and propagation is investigated in detail. The results indicate that the stiff nanoinhomogeneity suppresses nanocrack nucleation and propagation and thereby improves the tensile ductility of nanocomposites without loss of their predominantly high strength. Both the positive interface residual tension and interface elastic constants suppress nanocrack nucleation and propagation, while the negative interface residual tension and interface elastic constants promote nanocrack nucleation and propagation. Furthermore, the effect of interface residual tension is rather significant. The interface elastic constants have a weak effect on nanocrack nucleation and propagation. Full article

► Show Figures

Figure 1

18 pages, 2922 KiB

Open AccessArticle

A Hybrid Finite Element—Machine Learning Backward Training Approach to Analyze the Optimal Machining Conditions

by Kriz George, Sathish Kannan, Ali Raza and Salman Pervaiz

Materials 2021, 14(21), 6717; https://doi.org/10.3390/ma14216717 - 08 Nov 2021

Viewed by 1709

Abstract

As machining processes are complex in nature due to the involvement of large plastic strains occurring at higher strain rates, and simultaneous thermal softening of material, it is necessary for manufacturers to have some manner of determining whether the inputs will achieve the [...] Read more.

As machining processes are complex in nature due to the involvement of large plastic strains occurring at higher strain rates, and simultaneous thermal softening of material, it is necessary for manufacturers to have some manner of determining whether the inputs will achieve the desired outputs within the limitations of available resources. However, finite element simulations—the most common means to analyze and understand the machining of high-performance materials under various cutting conditions and environments—require high amounts of processing power and time in order to output reliable and accurate results which can lead to delays in the initiation of manufacture. The objective of this study is to reduce the time required prior to fabrication to determine how available inputs will affect the desired outputs and machining parameters. This study proposes a hybrid predictive methodology where finite element simulation data and machine learning are combined by feeding the time series output data generated by Finite Element Modeling to an Artificial Neural Network in order to acquire reliable predictions of optimal and/or expected machining inputs (depending on the application of the proposed approach) using what we describe as a backwards training model. The trained network was then fed a test dataset from the simulations, and the results acquired show a high degree of accuracy with regards to cutting force and depth of cut, whereas the predicted/expected feed rate was wildly inaccurate. This is believed to be due to either a limited dataset or the much stronger effect that cutting speed and depth of cut have on power, cutting forces, etc., as opposed to the feed rate. It shows great promise for further research to be performed for implementation in manufacturing facilities for the generation of optimal inputs or the real-time monitoring of input conditions to ensure machining conditions do not vary beyond the norm during the machining process. Full article

(This article belongs to the Special Issue Intelligent Machining: Process Optimisation)

► Show Figures

Figure 1

13 pages, 2970 KiB

Open AccessArticle

Study of Construction and Performance on Photoelectric Devices of Cs–Pb–Br Perovskite Quantum Dot

by Shiyu Ma, Yan Lu, Bo Wang and Jinkai Li

Materials 2021, 14(21), 6716; https://doi.org/10.3390/ma14216716 - 08 Nov 2021

Cited by 1 | Viewed by 1572

Abstract

White LEDs were encapsulated using Cs₄PbBr₆ quantum dots and Gd₂O₃:Eu red phosphor as lamp powder. Under the excitation of a GaN chip, the color coordinates of the W-LED were (0.33, 0.34), and the color temperature was [...] Read more.

White LEDs were encapsulated using Cs₄PbBr₆ quantum dots and Gd₂O₃:Eu red phosphor as lamp powder. Under the excitation of a GaN chip, the color coordinates of the W-LED were (0.33, 0.34), and the color temperature was 5752 K, which is close to the color coordinate and color temperature range of standard sunlight. The electric current stability was excellent with an increase in the electric current, voltage, and luminescence intensity of the quantum dots and phosphors by more than 10 times. However, the stability of the quantum dots was slightly insufficient over long working periods. The photocatalytic devices were constructed using TiO₂, CsPbBr₃, and NiO as an electron transport layer, light absorption layer, and catalyst, respectively. The Cs–Pb–Br-based perovskite quantum dot photocatalytic devices were constructed using a two-step spin coating method, one-step spin coating method, and full PLD technology. In order to improve the water stability of the device, a hydrophobic carbon paste and carbon film were selected as the hole transport layer. The TiO₂ layer and perovskite layer with different thicknesses and film forming qualities were obtained by changing the spin coating speed. The influence of the spin coating speed on the device’s performance was explored through SEM and a J–V curve to find the best spin coating process. The device constructed by the two-step spin coating method had a higher current density but no obvious increase in the current density under light, while the other two methods could obtain a more obvious light response, but the current density was very low. Full article

(This article belongs to the Special Issue Emerging Materials and Systems for Electrochemical Energy Storage Application)

► Show Figures

Figure 1

16 pages, 3714 KiB

Open AccessArticle

Snow Melting Performance of Graphene Composite Conductive Concrete in Severe Cold Environment

by Xinjie Wang, Yongkang Wu, Pinghua Zhu and Tao Ning

Materials 2021, 14(21), 6715; https://doi.org/10.3390/ma14216715 - 08 Nov 2021

Cited by 11 | Viewed by 2332

Abstract

The use of conductive concrete is an effective way to address snow and ice accretion on roads in cold regions because of its energy saving and high efficiency without interruption of traffic. Composite conductive concrete was prepared using graphene, carbon fiber, and steel [...] Read more.

The use of conductive concrete is an effective way to address snow and ice accretion on roads in cold regions because of its energy saving and high efficiency without interruption of traffic. Composite conductive concrete was prepared using graphene, carbon fiber, and steel fiber, and the optimum dosage of graphene was explored with resistivity as the criterion. Subsequently, under the conditions of an initial temperature of −15 °C and a wind speed of 20 km/h, the extremely severe snow event environment in cold regions was simulated. The effects of electrode spacing and electric voltage on snow melting performance of conductive concrete slab were explored. Results showed that graphene can significantly improve the conductivity of conductive concrete; the optimal content of graphene was 0.4% of cement mass in terms of resistivity. The snow-melting power of conductive concrete slab decreased with increase in electrode spacing and increased with increase in on-voltage. For an optimal input voltage of 156 V and an optimal electrode spacing of 10 cm, the time required to melt a 24 h snow thickness (21 cm), accumulated during a simulated severe snow event, was only 2 h, which provides an empirical basis for the application of graphene composite conductive concrete to pavement snow melting in cold regions. Full article

(This article belongs to the Topic Fiber-Reinforced Cementitious Composites)

► Show Figures

Figure 1

16 pages, 7594 KiB

Open AccessArticle

Thermochemical Laser-Induced Periodic Surface Structures Formation by Femtosecond Laser on Hf Thin Films in Air and Vacuum

by Dmitrij A. Belousov, Kirill A. Bronnikov, Konstantin A. Okotrub, Sergey L. Mikerin, Victor P. Korolkov, Vadim S. Terentyev and Alexander V. Dostovalov

Materials 2021, 14(21), 6714; https://doi.org/10.3390/ma14216714 - 08 Nov 2021

Cited by 6 | Viewed by 2299

Abstract

Thermochemical laser-induced periodic surface structures (TLIPSS) are a relatively new type of periodic structures formed in the focal area of linear polarized laser radiation by the thermally stimulated reaction of oxidation. The high regularity of the structures and the possibility of forming high-ordered [...] Read more.

Thermochemical laser-induced periodic surface structures (TLIPSS) are a relatively new type of periodic structures formed in the focal area of linear polarized laser radiation by the thermally stimulated reaction of oxidation. The high regularity of the structures and the possibility of forming high-ordered structures over a large area open up possibilities for the practical application for changing the optical and physical properties of materials surface. Since the mechanism of formation of these structures is based on a chemical oxidation reaction, an intriguing question involves the influence of air pressure on the quality of structure formation. This paper presents the results on the TLIPSS formation on a thin hafnium film with fs IR laser radiation at various ambient air pressures from 4 Torr to 760 Torr. Despite the decrease in the oxygen content in the ambient environment by two orders of magnitude, the formation of high-ordered TLIPSS (dispersion in the LIPSS orientation angle δθ < 5°) with a period of ≈700 nm occurs within a wide range of parameters variation (laser power, scanning speed). This behavior of TLIPSS formation is in agreement with experimental data obtained earlier on the study of the kinetics of high-temperature oxidation of hafnium at various oxygen pressures. Full article

► Show Figures

Figure 1

14 pages, 3414 KiB

Open AccessArticle

Development of Machine Learning Models to Evaluate the Toughness of OPH Alloys

by Omid Khalaj, Moslem Ghobadi, Ehsan Saebnoori, Alireza Zarezadeh, Mohammadreza Shishesaz, Bohuslav Mašek, Ctibor Štadler and Jiří Svoboda

Materials 2021, 14(21), 6713; https://doi.org/10.3390/ma14216713 - 08 Nov 2021

Cited by 4 | Viewed by 1785

Abstract

Oxide Precipitation-Hardened (OPH) alloys are a new generation of Oxide Dispersion-Strengthened (ODS) alloys recently developed by the authors. The mechanical properties of this group of alloys are significantly influenced by the chemical composition and appropriate heat treatment (HT). The main steps in producing [...] Read more.

Oxide Precipitation-Hardened (OPH) alloys are a new generation of Oxide Dispersion-Strengthened (ODS) alloys recently developed by the authors. The mechanical properties of this group of alloys are significantly influenced by the chemical composition and appropriate heat treatment (HT). The main steps in producing OPH alloys consist of mechanical alloying (MA) and consolidation, followed by hot rolling. Toughness was obtained from standard tensile test results for different variants of OPH alloy to understand their mechanical properties. Three machine learning techniques were developed using experimental data to simulate different outcomes. The effectivity of the impact of each parameter on the toughness of OPH alloys is discussed. By using the experimental results performed by the authors, the composition of OPH alloys (Al, Mo, Fe, Cr, Ta, Y, and O), HT conditions, and mechanical alloying (MA) were used to train the models as inputs and toughness was set as the output. The results demonstrated that all three models are suitable for predicting the toughness of OPH alloys, and the models fulfilled all the desired requirements. However, several criteria validated the fact that the adaptive neuro-fuzzy inference systems (ANFIS) model results in better conditions and has a better ability to simulate. The mean square error (MSE) for artificial neural networks (ANN), ANFIS, and support vector regression (SVR) models was 459.22, 0.0418, and 651.68 respectively. After performing the sensitivity analysis (SA) an optimized ANFIS model was achieved with a MSE value of 0.003 and demonstrated that HT temperature is the most significant of these parameters, and this acts as a critical rule in training the data sets. Full article

(This article belongs to the Special Issue Non-conventional Machining of Hard Materials)

► Show Figures

Figure 1

17 pages, 4831 KiB

Open AccessArticle

Compressive Behavior, Microstructural Properties, and Freeze–Thaw Behavior of Tailing Recycled Aggregate Concrete with Waste Polypropylene Fiber Addition

by Fan Xu, Tao Li, Chenghua Li, Zhijun Li, Sheliang Wang and Nan Zhao

Materials 2021, 14(21), 6712; https://doi.org/10.3390/ma14216712 - 08 Nov 2021

Cited by 8 | Viewed by 1489

Abstract

To improve the high brittleness of recycled aggregate concrete containing iron ore tailings (TRAC), the feasibility of adding polypropylene fiber (PPF) to TRAC was studied by performing a compression stress–strain curve test, scanning electron microscope characterization, and a freeze–thaw cycle test. The results [...] Read more.

To improve the high brittleness of recycled aggregate concrete containing iron ore tailings (TRAC), the feasibility of adding polypropylene fiber (PPF) to TRAC was studied by performing a compression stress–strain curve test, scanning electron microscope characterization, and a freeze–thaw cycle test. The results indicated that PPF had a beneficial impact on reducing the brittleness of TRAC. With the increase in PPF content, the peak strain increased, the elastic modulus decreased, and the peak stress and energy absorption capacity increased at first and then decreased. Furthermore, the microstructure investigation revealed that the interface friction between the PPF, aggregate, and cement matrix was the main source of energy dissipation. When the load acted on the concrete, the stress was dispersed to the fiber monofilaments, thus effectively enhancing the peak stress and peak strain of concrete and suppressing the generation and development of cracks in the concrete. In terms of freeze–thaw resistance, adding a small amount of PPF could reduce the negative effects of the freeze–thaw process on the cement matrix. On the premise of ensuring strength, the waste utilization should be as high as possible. Therefore, it was suggested that the content of PPF in fiber-reinforced tailings recycled aggregate concrete (TRAC-PP) should be 0.6%. Full article

► Show Figures

Figure 1

15 pages, 3338 KiB

Open AccessArticle

Structural Retrofitting of Corroded Reinforced Concrete Beams Using Bamboo Fiber Laminate

by Paul Oluwaseun Awoyera, Tobechukwu Austin Nworgu, Balaji Shanmugam, Krishna Prakash Arunachalam, Iman Mansouri, Lenin Miguel Bendezu Romero and Jong-Wan Hu

Materials 2021, 14(21), 6711; https://doi.org/10.3390/ma14216711 - 08 Nov 2021

Cited by 12 | Viewed by 2776

Abstract

Corrosion creates a significant degradation mechanism in reinforced concrete (RC) structures, which would require a high cost of maintenance and repair in affected buildings. However, as the cost of repairing corrosion-damaged structures is high, it is therefore pertinent to develop alternative eco-friendly and [...] Read more.

Corrosion creates a significant degradation mechanism in reinforced concrete (RC) structures, which would require a high cost of maintenance and repair in affected buildings. However, as the cost of repairing corrosion-damaged structures is high, it is therefore pertinent to develop alternative eco-friendly and sustainable methods. In this study, structural retrofitting of corroded reinforced concrete beams was performed using bamboo fiber laminate. Three reinforced normal weight concrete beams were produced, two of which were exposed to laboratory simulated corrosion medium, and the remaining one sample served as control. Upon completion of the corrosion cycle, one of the two corroded beams was retrofitted externally with a prefabricated bamboo fiber laminate by bonding the laminate to the beam surface with the aid of an epoxy resin. The three beams were subjected to loading on a four-point ultimate testing machine, and the loads with corresponding deflections were recorded through the entire load cycle of the beams. Finally, the mass loss of embedded steel reinforcements was determined to measure the effect of corrosion on the beams and the steel. The result showed that corroded beams strengthened with bamboo laminates increase the bearing capacity. Using a single bamboo laminate in the tensile region of the corroded beam increased the ultimate load capacity of the beam up to 21.1% than the corroded beam without retrofit. It was demonstrated in this study that the use of bamboo fiber polymer for strengthening destressed RC beams is a more sustainable approach than the conventional synthetic fibers. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

► Show Figures

Figure 1

21 pages, 12124 KiB

Open AccessArticle

Facile Fabrication of Novel NiFe₂O₄@Carbon Composites for Enhanced Adsorption of Emergent Antibiotics

by Van Tan Lam, Thi Cam Quyen Ngo and Long Giang Bach

Materials 2021, 14(21), 6710; https://doi.org/10.3390/ma14216710 - 08 Nov 2021

Cited by 6 | Viewed by 1930

Abstract

Water purification is becoming one of the most pertinent environmental issues throughout the world. Among common types of water pollution involving heavy metals, pharmaceutical drugs, textile dyes, personal care products, and other persistent organic pollutants, the pollution of antibiotic drugs is increasingly emerging [...] Read more.

Water purification is becoming one of the most pertinent environmental issues throughout the world. Among common types of water pollution involving heavy metals, pharmaceutical drugs, textile dyes, personal care products, and other persistent organic pollutants, the pollution of antibiotic drugs is increasingly emerging due to their adverse effects on microorganisms, aquatic animals, and human health. Therefore, the treatment of such contaminants is very necessary to reduce the concentration of antibiotic pollutants to permissible levels prior to discharge. Herein, we report the use of NiFe₂O₄@C composites from a bimetallic-based metal-organic framework Ni-MIL-88B(Fe) for removal of ciprofloxacin (CFX) and tetracycline (TCC). The effect of production temperatures (600–900 °C), solution pH (2–10), NiFe₂O₄@C dose (0.05–0.2 g/L), concentration of antibiotics (10–60 mg/L), and uptake time (0–480 min) was investigated systematically. Response surface methodology and central composite design were applied for quadratic models to discover optimum conditions of antibiotic adsorption. With high coefficients of determination (R² = 0.9640–0.9713), the proposed models were significant statistically. Under proposed optimum conditions, the adsorption capacity for CFX and TCC were found at 256.244, and 105.38 mg/g, respectively. Recyclability study was employed and found that NiFe₂O₄@C-900 could be reused for up to three cycles, offering the potential of this composite as a good adsorbent for removal of emergent antibiotics. Full article

(This article belongs to the Special Issue Environmentally-Friendly Materials in Wastewater Treatment)

► Show Figures

Figure 1

17 pages, 4033 KiB

Open AccessArticle

Study on the Strength and Micro Characteristics of Grouted Specimens with Different Superfine Cement Contents

by Dongyue Zhang, Zhenqian Ma, Yihuai Zou, Hongfei Xie and Ruichong Guan

Materials 2021, 14(21), 6709; https://doi.org/10.3390/ma14216709 - 08 Nov 2021

Cited by 6 | Viewed by 1438

Abstract

To provide the most effective comprehensive performance grouting material ratio, in this experimental investigation, a total of eight grouted specimens with two water-cement ratios (0.45:1, 0.55:1) and four different superfine cement contents (0%, 30%, 70%, 100%) were evaluated. Based on a uniaxial compression [...] Read more.

To provide the most effective comprehensive performance grouting material ratio, in this experimental investigation, a total of eight grouted specimens with two water-cement ratios (0.45:1, 0.55:1) and four different superfine cement contents (0%, 30%, 70%, 100%) were evaluated. Based on a uniaxial compression test, the fractal dimension of the fragments, a mercury injection test, and scanning electron microscopy, the effects of the superfine cement content on the strength characteristics and microscopic characteristics of the grouted specimens were studied. The results showed that increasing the superfine cement content could enhance the compressive and tensile strength of the grouted specimens and reduce the fractal dimension of the fragments and the porosity of the grouted specimens. The superfine cement content increased from 0% to 70% when the water-cement ratio was 0.45:1. The compressive strength of the grouted specimens increased from 16.7 MPa to 26.3 MPa, and the fractal dimension decreased from 1.8645 to 1.2301. When the water-cement ratio was 0.55:1, the compressive strength of the grouted specimens increased from 10.5 MPa to 20.6 MPa, and the fractal dimension value decreased from 2.2955 to 1.4458. When the superfine cement content increased from 0% to 100%, the water-cement ratio was 0.45:1. The porosity of the grouted specimens was reduced from 28.41% to 21.62%. When the water-cement ratio was 0.55:1, the porosity of the grouted specimens was reduced from 33.33% to 29.46%. Full article

► Show Figures

Figure 1

15 pages, 3485 KiB

Open AccessArticle

Assessment of the Possibility of Using Fly Ash from Biomass Combustion for Concrete

by Jakub Jura and Malgorzata Ulewicz

Materials 2021, 14(21), 6708; https://doi.org/10.3390/ma14216708 - 07 Nov 2021

Cited by 22 | Viewed by 2187

Abstract

This article analyses the possibility of using fly ash from the combustion of wood–sunflower biomass in a fluidized bed boiler as an additive to concrete. The research shows that fly ash applied in an amount of 10–30% can be added as a sand [...] Read more.

This article analyses the possibility of using fly ash from the combustion of wood–sunflower biomass in a fluidized bed boiler as an additive to concrete. The research shows that fly ash applied in an amount of 10–30% can be added as a sand substitute for the production of concrete, without reducing quality (compression strength and low-temperature resistance) compared to control concrete. The 28-day compressive strength of concrete with fly ash increases with the amount of ash added (up to 30%), giving a strength 28% higher than the control concrete sample. The addition of fly ash reduces the extent to which the compression strength of concrete is lowered after low-temperature resistance tests by 22–82%. The addition of fly ash in the range of 10–30% causes a slight increase in the water absorption of concrete. Concretes containing the addition of fly ash from biomass combustion do not have a negative environmental impact with respect to the leaching of heavy metal ions into the environment. Full article

(This article belongs to the Special Issue Recycled Materials in Civil Engineering Application)

► Show Figures

Figure 1

29 pages, 2979 KiB

Open AccessReview

Carbon Nanotubes: Current Perspectives on Diverse Applications in Targeted Drug Delivery and Therapies

by Mohamed Rahamathulla, Rohit R. Bhosale, Riyaz A. M. Osmani, Kasturi C. Mahima, Asha P. Johnson, Umme Hani, Mohammed Ghazwani, Mohammed Y. Begum, Sultan Alshehri, Mohammed M. Ghoneim, Faiyaz Shakeel and Hosahalli V. Gangadharappa

Materials 2021, 14(21), 6707; https://doi.org/10.3390/ma14216707 - 07 Nov 2021

Cited by 40 | Viewed by 3531

Abstract

Current discoveries as well as research findings on various types of carbon nanostructures have inspired research into their utilization in a number of fields. These carbon nanostructures offer uses in pharmacy, medicine and different therapies. One such unique carbon nanostructure includes carbon nanotubes [...] Read more.

Current discoveries as well as research findings on various types of carbon nanostructures have inspired research into their utilization in a number of fields. These carbon nanostructures offer uses in pharmacy, medicine and different therapies. One such unique carbon nanostructure includes carbon nanotubes (CNTs), which are one-dimensional allotropes of carbon nanostructure that can have a length-to-diameter ratio greater than 1,000,000. After their discovery, CNTs have drawn extensive research attention due to their excellent material properties. Their physical, chemical and electronic properties are excellent and their composites provide great possibilities for enormous nanometer applications. The current study provides a systematic review based on prior literature review and data gathered from various sources. The various research studies from many research labs and organizations were systematically retrieved, collected, compiled and written. The entire collection and compilation of this review concluded the use of CNT approaches and their efficacy and safety for the treatment of various diseases such as brain tumors or cancer via nanotechnology-based drug delivery, phototherapy, gene therapy, antiviral therapy, antifungal therapy, antibacterial therapy and other biomedical applications. The current review covers diverse applications of CNTs in designing a range of targeted drug delivery systems and application for various therapies. It concludes with a discussion on how CNTs based medicines can expand in the future. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

► Show Figures

Figure 1

14 pages, 2751 KiB

Open AccessArticle

Hygric Properties of Machine-Made, Historic Clay Bricks from North-Eastern Poland (Former East Prussia): Characterization and Specification for Replacement Materials

by Maria Tunkiewicz, Joanna Misiewicz, Pawel Sikora and Sang-Yeop Chung

Materials 2021, 14(21), 6706; https://doi.org/10.3390/ma14216706 - 07 Nov 2021

Cited by 3 | Viewed by 2111

Abstract

This paper deals with the hygric characterization of early 20th century machine-made clay bricks, representative of great number of historical buildings in north-eastern Poland. Heritage buildings have a high potential for adaptive reuse, which is strictly connected with an urge for knowledge about [...] Read more.

This paper deals with the hygric characterization of early 20th century machine-made clay bricks, representative of great number of historical buildings in north-eastern Poland. Heritage buildings have a high potential for adaptive reuse, which is strictly connected with an urge for knowledge about the properties of these existing building envelopes. To better understand the hygric behavior of historic buildings, various experimental laboratory tests, including density, water absorption, compressive strength and freeze-thaw resistance, were conducted. In order to assess the microstructural characteristics of the tested bricks, mercury intrusion porosimetry (MIP) and X-ray micro-computed tomography (micro-CT) tests were performed. These tests were conducted on clay bricks from historic buildings, as well as on those that are currently being produced, in order to identify the relationship between the materials used in the past and the replacements produced presently. This paper addresses the lack of systematic application of existing standards for evaluating the state of the conservation of historic bricks and for establishing the specifications for replacement bricks. The results of conducted study and further research will be the basis for creating a historic materials database. It would be a useful tool for selecting bricks that correspond with the historically used materials and help to maintain homogenous structure of the restored buildings. Full article

(This article belongs to the Special Issue Advanced Construction Materials and Processes in Poland)

► Show Figures

Figure 1

12 pages, 6449 KiB

Open AccessArticle

Effect of Grain Refiner on Fracture Toughness of 7050 Ingot and Plate

by Fang Yu, Xiangjie Wang, Tongjian Huang and Daiyi Chao

Materials 2021, 14(21), 6705; https://doi.org/10.3390/ma14216705 - 07 Nov 2021

Cited by 6 | Viewed by 1687

Abstract

In this paper, two types of grain refining alloys, Al-3Ti-0.15C and Al-5Ti-0.2B, were used to cast two types of 7050 rolling ingots. The effect of Al-3Ti-0.15C and Al-5Ti-0.2B grain refiners on fracture toughness in different directions for 7050 ingots after heat treatment and [...] Read more.

In this paper, two types of grain refining alloys, Al-3Ti-0.15C and Al-5Ti-0.2B, were used to cast two types of 7050 rolling ingots. The effect of Al-3Ti-0.15C and Al-5Ti-0.2B grain refiners on fracture toughness in different directions for 7050 ingots after heat treatment and 7050-T7651 plates was investigated using optical electron microscopy (OEM) and scanning electron microscopy (SEM). Mechanical properties testing included both tensile and plane strain fracture toughness (K_IC). The grain size was measured from the surface to the center of the 7050 ingots with two different grain refiners. The fracture surface was analyzed by SEM and energy dispersive spectrometer (EDS). The experiments showed the grain size from edge to center was reduced in 7050 ingots with both the TiC and TiB refiners, and the grain size was larger for ingots with the Al-3Ti-0.15C grain refiner at the same position. The tensile properties of 7050 ingots after heat treatment with Al-3Ti-0.15C grain refiner were 1–2 MPa lower than the ingot with the Al-5Ti-0.2B grain refiner. For the 7050-T7651 100 mm thick plate with the Al-3Ti-0.15C grain refiner, for the L direction, the tensile properties were lower by about 10~15 MPa; for the plate with the Al-3Ti-0.15C refiner than plate with Al-5Ti-0.2B refiner, for the LT direction, the tensile properties were lower by about 13–18 MPa; and for the ST direction, they were lower by about 8–10 MPa compared to that of Al-5Ti-0.2B refiner. The fracture toughness of the 7050-T7651 plate produced using the Al-3Ti-0.15C ingot was approximately 2–6 MPa ·

\sqrt{m}

higher than the plate produced from the Al-5Ti-0.2B ingot. Fractography of the failed fracture toughness specimens revealed that the path of crack propagation of the 7050 ingot after heat treatment produced from the Al-3Ti-0.15C grain refiner was more tortuous than in the ingot produced from the Al-5Ti-0.2B, which resulted in higher fracture toughness. Full article

(This article belongs to the Special Issue Advances in High-Performance Non-ferrous Materials)

► Show Figures

Figure 1

12 pages, 2000 KiB

Open AccessArticle

Influence of Alloy Atoms on Substitution Properties of Hydrogen by Helium in ZrCoH₃

by Panpan Wang, Qilong Cao, Yuwei You, Xiangshan Kong, Xuebang Wu and Changsong Liu

Materials 2021, 14(21), 6704; https://doi.org/10.3390/ma14216704 - 07 Nov 2021

Cited by 2 | Viewed by 1433

Abstract

Intermetallic alloy ZrCo is a good material for storing tritium (T). However, ZrCo is prone to disproportionation reactions during the process of charging and discharging T. Alloying atoms are often added in ZrCo, occupying the Zr or Co site, in order to restrain [...] Read more.

Intermetallic alloy ZrCo is a good material for storing tritium (T). However, ZrCo is prone to disproportionation reactions during the process of charging and discharging T. Alloying atoms are often added in ZrCo, occupying the Zr or Co site, in order to restrain disproportionation reactions. Meanwhile, T often decays into helium (He), and the purity of T seriously decreases once He escapes from ZrCo. Therefore, it is necessary to understand the influence of alloying atoms on the basic stability property of He. In this work, we perform systematical ab initio calculations to study the stability property of He in ZrCoH₃ (ZrCo adsorbs the H isotope, forming ZrCoH₃). The results suggest that the He atom will undergo displacements of 0.31 and 0.12 Å when it substitutes for Co and Zr, respectively. In contrast, the displacements are very large, at 0.67–1.09 Å, for He replacing H. Then, we introduce more than 20 alloying atoms in ZrCo to replace Co and Zr in order to examine the influence of alloying atoms on the stability of He at H sites. It is found that Ti, V, Cr, Mn, Fe, Zn, Nb, Mo, Tc, Ru, Ta, W, Re, and Os replacing Co can increase the substitution energy of H by the He closest to the alloying atom, whereas only Cr, Mn, Fe, Mo, Tc, Ru, Ta, W, Re, and Os replacing Co can increase the substitution energy of H by the He next closest to the alloying atom. The influence of the alloying atom substituting Zr site on the substitution energies is inconspicuous, and only Nb, Mo, Ru, Ta, and W increase the substitution energies of H by the He closest to the alloying atom. The increase in the substitution energy may suggest that these alloy atoms are conducive to fix the He atom in ZrCo and avoid the reduction in tritium purity. Full article

(This article belongs to the Special Issue Experiment and Calculation Simulation to Study Hydrogen-Helium Effect Mechanism in Materials)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Materials, Volume 14, Issue 21 (November-1 2021) – 505 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI