Materials

18 pages, 7243 KiB

Open AccessArticle

Near-Infrared Light-Responsive Shell-Crosslinked Micelles of Poly(d,l-lactide)-b-poly((furfuryl methacrylate)-co-(N-acryloylmorpholine)) Prepared by Diels–Alder Reaction for the Triggered Release of Doxorubicin

by Sonyabapu Yadav, Kalyan Ramesh, Parveen Kumar, Sung-Han Jo, Seong II Yoo, Yeong-Soon Gal, Sang-Hyug Park and Kwon Taek Lim

Materials 2021, 14(24), 7913; https://doi.org/10.3390/ma14247913 - 20 Dec 2021

Cited by 11 | Viewed by 4116

Abstract

In the present study, we developed near-infrared (NIR)-responsive shell-crosslinked (SCL) micelles using the Diels–Alder (DA) click reaction between an amphiphilic copolymer poly(d,l-lactide)₂₀-b-poly((furfuryl methacrylate)₁₀-co-(N-acryloylmorpholine)₇₈) (PLA₂₀-b [...] Read more.

In the present study, we developed near-infrared (NIR)-responsive shell-crosslinked (SCL) micelles using the Diels–Alder (DA) click reaction between an amphiphilic copolymer poly(d,l-lactide)₂₀-b-poly((furfuryl methacrylate)₁₀-co-(N-acryloylmorpholine)₇₈) (PLA₂₀-b-P(FMA₁₀-co-NAM₇₈)) and a diselenide-containing crosslinker, bis(maleimidoethyl) 3,3′-diselanediyldipropionoate (BMEDSeDP). The PLA₂₀-b-P(FMA₁₀-co-NAM₇₈) copolymer was synthesized by RAFT polymerization of FMA and NAM using a PLA₂₀-macro-chain transfer agent (PLA₂₀-CTA). The DA reaction between BMEDSeDP and the furfuryl moieties in the copolymeric micelles in water resulted in the formation of SCL micelles. The SCL micelles were analyzed by ¹H-NMR, FE-SEM, and DLS. An anticancer drug, doxorubicin (DOX), and an NIR sensitizer, indocyanine green (ICG), were effectively incorporated into the SCL micelles during the crosslinking reaction. The DOX/ICG-loaded SCL micelles showed pH- and NIR-responsive drug release, where burst release was observed under NIR laser irradiation. The in vitro cytotoxicity analysis demonstrated that the SCL was not cytotoxic against normal HFF-1 cells, while DOX/ICG-loaded SCL micelles exhibited significant antitumor activity toward HeLa cells. Thus, the SCL micelles of PLA₂₀-b-P(FMA₁₀-co-NAM₇₈) can be used as a potential delivery vehicle for the controlled drug release in cancer therapy. Full article

(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Polymers)

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16 pages, 3543 KiB

Open AccessArticle

A Ru/RuO₂-Doped TiO₂ Nanotubes as pH Sensors for Biomedical Applications: The Effect of the Amount and Oxidation of Deposited Ru on the Electrochemical Response

by Nikola Macháčková, Jitřenka Jírů, Vojtěch Hybášek and Jaroslav Fojt

Materials 2021, 14(24), 7912; https://doi.org/10.3390/ma14247912 - 20 Dec 2021

Cited by 4 | Viewed by 2595

Abstract

In the field of orthopedic or dental implants, titanium and its alloys are most commonly used because of their excellent mechanical and corrosion properties and good biocompatibility. After implantation into the patient’s body, there is a high risk of developing bacterial inflammation, which [...] Read more.

In the field of orthopedic or dental implants, titanium and its alloys are most commonly used because of their excellent mechanical and corrosion properties and good biocompatibility. After implantation into the patient’s body, there is a high risk of developing bacterial inflammation, which negatively affects the surrounding tissues and the implant itself. Early detection of inflammation could be done with a pH sensor. In this work, pH-sensitive systems based on TiO₂-Ru and TiO₂-RuO₂ combinations were fabricated and investigated. As a base material, Ti-6Al-4V alloy nanostructured by anodic oxidation was used. Ruthenium was successfully deposited on nanotubular TiO₂ using cyclic polarization, galvanostatic and potentiostatic mode. Potentiostatic mode proved to be the most suitable. The selected samples were oxidized by cyclic polarization to form a TiO₂-RuO₂ system. The success of the oxidation was confirmed by XPS analysis. The electrochemical response of the systems to pH change was measured in saline solution using different techniques. The measurement of open circuit potential showed that unoxidized samples (TiO₂-Ru) exhibited sub-Nernstian behavior (39.2 and 35.8 mV/pH). The oxidized sample (TiO₂-RuO₂) containing the highest amount of Ru exhibited super-Nernstian behavior (67.3 mV/pH). The Mott–Schottky analysis proved to be the best method. The use of the electrochemical impedance method can also be considered, provided that greater stability of the samples is achieved. Full article

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18 pages, 7939 KiB

Open AccessArticle

Pitting Corrosion Behavior and Surface Microstructure of Copper Strips When Rolled with Oil-in-Water Emulsions

by Xudong Yan and Jianlin Sun

Materials 2021, 14(24), 7911; https://doi.org/10.3390/ma14247911 - 20 Dec 2021

Cited by 1 | Viewed by 3174

Abstract

Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. [...] Read more.

Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. It was found that the corrosion current densities of the rolled Cu strips increased with accumulated reduction, which also lowered the pitting potentials and weakened their corrosion resistances. Therefore, the corrosive tendency of Cu strips under different rolling reductions (ε) followed the order of ε_0% < ε_20.7% < ε_50.6% < ε_77.3%. The Cu surface easily reacted with chlorine, sulfur, and carbon components from O/W emulsions to generate pitting corrosion. Under the interactive effect of pitting corrosion and stress corrosion, pits expanded along the rolling direction. The aggregation of anions in surface defects, such as dislocations, metastable pits, and microcracks, further accelerated the pitting corrosion of the surface. Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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18 pages, 27869 KiB

Open AccessArticle

A Fully 3D-Printed Steerable Instrument for Minimally Invasive Surgery

by Costanza Culmone, Kirsten Lussenburg, Joost Alkemade, Gerwin Smit, Aimée Sakes and Paul Breedveld

Materials 2021, 14(24), 7910; https://doi.org/10.3390/ma14247910 - 20 Dec 2021

Cited by 13 | Viewed by 5693

Abstract

In the field of medical instruments, additive manufacturing allows for a drastic reduction in the number of components while improving the functionalities of the final design. In addition, modifications for users’ needs or specific procedures become possible by enabling the production of single [...] Read more.

In the field of medical instruments, additive manufacturing allows for a drastic reduction in the number of components while improving the functionalities of the final design. In addition, modifications for users’ needs or specific procedures become possible by enabling the production of single customized items. In this work, we present the design of a new fully 3D-printed handheld steerable instrument for laparoscopic surgery, which was mechanically actuated using cables. The pistol-grip handle is based on ergonomic principles and allows for single-hand control of both grasping and omnidirectional steering, while compliant joints and snap-fit connectors enable fast assembly and minimal part count. Additive manufacturing allows for personalization of the handle to each surgeon’s needs by adjusting specific dimensions in the CAD model, which increases the user’s comfort during surgery. Testing showed that the forces on the instrument handle required for steering and grasping were below 15 N, while the grasping force efficiency was calculated to be 10–30%. The instrument combines the advantages of additive manufacturing with regard to personalization and simplified assembly, illustrating a new approach to the design of advanced surgical instruments where the customization for a single procedure or user’s need is a central aspect. Full article

(This article belongs to the Collection 3D Printing in Medicine and Biomedical Engineering)

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13 pages, 5322 KiB

Open AccessArticle

Influence of Flux and Related Factors on Intermetallic Layer Growth within SAC305 Solder Joints

by Karel Dušek, Petr Veselý, David Bušek, Adam Petráč, Attila Géczy, Balázs Illés and Oliver Krammer

Materials 2021, 14(24), 7909; https://doi.org/10.3390/ma14247909 - 20 Dec 2021

Cited by 7 | Viewed by 3346

Abstract

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and [...] Read more.

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and OSP/HASL/ENIG soldering pad surface finish. Two original SAC305 solder pastes differing only in the used flux were chosen for the experiment. The influence of multiple reflows was also observed. The intermetallic layer thicknesses were obtained by the image analysis of micro-section images. The flux type proved to have a significant impact on the intermetallic layer thickness. The solder paste with ROL1 caused an increase in IML thickness by up to 40% in comparison to an identical paste with ROL0 flux. Furthermore, doubling the roughness of the solder mask has increased the resulting IML thickness by 37% at HASL surface finish and by an average of 22%. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Preparation, Properties and Applications)

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33 pages, 71636 KiB

Open AccessArticle

Spent Graphite from End-of-Life Lithium-Ion Batteries (LIBs) as a Promising Nanoadditive to Boost Road Pavement Performance

by Nader Nciri, Namho Kim and Namjun Cho

Materials 2021, 14(24), 7908; https://doi.org/10.3390/ma14247908 - 20 Dec 2021

Cited by 9 | Viewed by 2712

Abstract

To take swift action towards tackling the global pollution crisis of discarded lithium-ion batteries (LIBs) while reinforcing road structures, this investigation was undertaken. The influence of various proportions of spent graphite (e.g., 5, 10, and 15 wt.% SG), harvested from end-of-life LIBs, on [...] Read more.

To take swift action towards tackling the global pollution crisis of discarded lithium-ion batteries (LIBs) while reinforcing road structures, this investigation was undertaken. The influence of various proportions of spent graphite (e.g., 5, 10, and 15 wt.% SG), harvested from end-of-life LIBs, on the performance of base AP-5 asphalt cement was studied. Multiple laboratory techniques have been employed to characterize the internal physiochemical interaction between the additive and the binder. These techniques include: elemental analysis (EA), thin-layer chromatography-flame ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), empirical test methods (e.g., penetration, softening point, viscosity, and ductility), dynamic shear rheometer (DSR), and multiple stress-creep recovery (MSCR). Prior to aging, SARA analysis demonstrated that the incremental SG addition into the AP-5 bitumen reduced the contents of saturates, aromatics, and resins, and increased the proportion of asphaltenes. After aging, the saturated and aromatic hydrocarbons kept decreasing; however, the resins increased and the asphaltenes declined. Accordingly, this has brought a progressive shift tendency in the stable–colloidal system for all binders from sol-state towards sol-gel-state. FT-IR scan revealed that the SG has no apparent chemical interaction with the binder, and is endowed solely with filling effects. XRD diagnosis highlighted that the steady SG incorporation into the binder amplified its crystallinity; thereby boosting the thermomechanical properties of mastics. SEM imaging unveiled that the lower-dose of SG exhibited higher compatibility within the bitumen matrix; nevertheless, the intermediate/higher-doses made the binder body relatively rougher. DSR/MSCR/conventional tests indicated that when the asphalt is blended with the graphitic powder under unaged/aged conditions, it becomes stiffer, more viscous, and less cohesive; thereby rendering it more resistant to deformation but not to cracking. In summary, it is promisingly proven that the SG could be successfully used as an asphalt additive and could be beneficial for improving paving performance and mitigating the pollution caused by dead LIBs as well. Full article

(This article belongs to the Special Issue Novel Construction Materials for Sustainable Pavements)

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19 pages, 2426 KiB

Open AccessArticle

Numerical Modeling and Evaluation of PEM Used for Fuel Cell Vehicles

by Yousef Darvishi, Seyed Reza Hassan-Beygi, Payam Zarafshan, Khadijeh Hooshyari, Urszula Malaga-Toboła and Marek Gancarz

Materials 2021, 14(24), 7907; https://doi.org/10.3390/ma14247907 - 20 Dec 2021

Cited by 8 | Viewed by 2290

Abstract

The present study sought to analyze a novel type of polymer membrane fuel cell to be used in vehicles. The performance of the fuel cell was evaluated by modeling the types of production–consumption heat in the anode and cathode (including half-reaction heat, activation [...] Read more.

The present study sought to analyze a novel type of polymer membrane fuel cell to be used in vehicles. The performance of the fuel cell was evaluated by modeling the types of production–consumption heat in the anode and cathode (including half-reaction heat, activation heat, and absorption/desorption heat) and waterflood conditions. The meshing of flow channels was carried out by square cells and the governing equations were numerically discretized in the steady mode using the finite difference method followed by solving in MATLAB software. Based on the simulation results, the anodic absorption/desorption heat, anodic half-reaction heat, and cathodic activation heat are positive while the cathodic absorption/desorption heat and cathodic half-reaction heat show negative values. All heat values exhibit a decremental trend over the flow channel. Considering the effect of relative humidity, the relative humidity of the cathode showed no significant change while the anode relative humidity decreased along the flow channel. The velocity at the membrane layer was considerably lower, due to the smaller permeability coefficient of this layer compared to the gas diffusion and reactants (cathode) layers. Full article

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20 pages, 5961 KiB

Open AccessArticle

Fabrication of Polycrystalline Cubic Boron Nitride/Metal Composite Particles by Surface Metallization Followed by Electroless Deposition Technique

by Walid Mohamed Daoush, Turki Saad Alkhuraiji and Abdulrahman Dohymish Alshammri

Materials 2021, 14(24), 7906; https://doi.org/10.3390/ma14247906 - 20 Dec 2021

Cited by 1 | Viewed by 2002

Abstract

Polycrystalline cBN/copper composite abrasive particles were prepared by an electroless powder coating process. Ti metallization and tin/silver metallization techniques were used to improve the coating process by depositing an autocatalytic metallic layer on the surface of the cBN particles. Metallized, as well as [...] Read more.

Polycrystalline cBN/copper composite abrasive particles were prepared by an electroless powder coating process. Ti metallization and tin/silver metallization techniques were used to improve the coating process by depositing an autocatalytic metallic layer on the surface of the cBN particles. Metallized, as well as un-metallized, cBN particles were further coated by copper using electroless deposition. Electroless copper coating of un-metallized and metallized cBN particles by 90 wt.% of copper were achieved. The surface morphology, the composition and the crystalline phase identifications of the metallized cBN particles, as well as the 10 wt.% cBN /copper composite powders, were investigated by field emission scanning electron microscopy, an energy-dispersive spectrometer and an X-ray diffractometer. The results show that the surface of the Ti metalized and tin/Ag-metallized cBN particles were covered by the nanosized Ti or Ag layer, respectively, which enhanced the deposition of the copper during the electroless deposition bath. The results also showed that the deposited layer on the metallized cBN particles was composed mainly of metallic copper. The produced 10 wt.% cBN/copper composite particles also underwent thermo-gravimetric analysis to investigate its stability at high temperature. It was revealed that the Ti-metallized cBN/copper composite powder has higher stability at 800 °C under the environmental conditions than the tin/silver-metallized and the un-metallized cBN/copper composite particles, respectively. Full article

(This article belongs to the Special Issue Advanced Computational Technologies for Simulation of the Structure of Solids Ceramics)

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11 pages, 28366 KiB

Open AccessArticle

Method for Mitigating Stray Current Corrosion in Buried Pipelines Using Calcareous Deposits

by Sin-Jae Kang, Min-Sung Hong and Jung-Gu Kim

Materials 2021, 14(24), 7905; https://doi.org/10.3390/ma14247905 - 20 Dec 2021

Cited by 4 | Viewed by 1854

Abstract

Stray current corrosion in buried pipelines can cause serious material damage in a short period of time. However, the available methods for mitigating stray current corrosion are still insufficient. In this study, as a countermeasure against stray current corrosion, calcareous depositions were applied [...] Read more.

Stray current corrosion in buried pipelines can cause serious material damage in a short period of time. However, the available methods for mitigating stray current corrosion are still insufficient. In this study, as a countermeasure against stray current corrosion, calcareous depositions were applied to reduce the total amount of current flowing into pipelines and to prevent corrosion. This study examined the reduction of stray current corrosion via the formation of calcareous deposit layers, composed of Ca, Mg, and mixed Ca and Mg, at the current inflow area. To verify the deposited layers, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed. The electrochemical tests revealed that all three types of calcareous deposits were able to effectively act as current barriers, and that they decreased the inflow current at the cathodic site. Among the deposits, the CaCO₃ layer mitigated the stray current most effectively, as it was not affected by Mg(OH)₂, which interferes with the growth of CaCO₃. The calcium-based layer was very thick and dense, and it effectively blocked the inflowing stray current, compared with the other layers. Full article

(This article belongs to the Special Issue Corrosion Properties and Mechanism of Steels)

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23 pages, 12785 KiB

Open AccessArticle

A Method and Device for Automated Grinding of Small Ceramic Elements

by Wojciech Kacalak, Dariusz Lipiński, Filip Szafraniec and Błażej Bałasz

Materials 2021, 14(24), 7904; https://doi.org/10.3390/ma14247904 - 20 Dec 2021

Cited by 3 | Viewed by 1875

Abstract

The paper describes an automated method for grinding small ceramic elements using a hyperboloid wheel. The problem of automating the process of machining elements made of nonmagnetic materials with a small area and low height has been solved. Automation of the grinding process [...] Read more.

The paper describes an automated method for grinding small ceramic elements using a hyperboloid wheel. The problem of automating the process of machining elements made of nonmagnetic materials with a small area and low height has been solved. Automation of the grinding process was possible thanks to automatic clamping of workpieces in the machining zone and sequential processing by a specified number of grinding wheels. The workpieces were passed through successive machining zones. The division of the allowance of individual grinding wheels was made taking into account the characteristics of the workpieces and the requirements for the results of the machining. Obtaining a long grinding zone and the effect of automatic clamping of the workpieces was possible due to the inclination of the grinding wheel axis in relation to the plane of movement of the workpieces. Innovative aggregate grinding wheels were used for grinding. The aggregates containing diamond abrasive grains, connected with a metal bond, were embedded in the porous structure of the resin bond. The aggregates ensured high efficiency of grinding, and their developed surface contributed to good holding in the resin binder. The durability of grinding wheels was 64 h, which enables the machining of 76,000 ceramic elements. Full article

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22 pages, 25713 KiB

Open AccessReview

Dental Implants Inserted in Fresh Extraction Sockets versus Healed Sites: A Systematic Review and Meta-Analysis

by Adam Ibrahim and Bruno Ramos Chrcanovic

Materials 2021, 14(24), 7903; https://doi.org/10.3390/ma14247903 - 20 Dec 2021

Cited by 11 | Viewed by 3348

Abstract

The present review aimed to evaluate the difference of dental implant failure rates and marginal bone loss (MBL) between implants inserted in fresh extraction sockets or healed sites. Electronic search was undertaken in three databases, plus manual search of journals, including studies randomized [...] Read more.

The present review aimed to evaluate the difference of dental implant failure rates and marginal bone loss (MBL) between implants inserted in fresh extraction sockets or healed sites. Electronic search was undertaken in three databases, plus manual search of journals, including studies randomized or not. Meta-analyses were performed besides meta-regressions, in order to verify how the odds ratio (OR) and MBL were associated with follow-up time. The review included 163 publications. Altogether, there were 17,278 and 38,738 implants placed in fresh extraction sockets and healed sites, respectively. Pairwise meta-analyses showed that implants in sockets had a higher failure risk in comparison to healed sites: OR 1.349, all studies included; OR 2.070, only prospective non-RCTs; OR 2.487, only RCTs (all p < 0.001). The difference in implant failure between the groups was statistically significant in the maxilla (OR 1.616, p = 0.029), but not in the mandible (OR 2.192, p = 0.075). The MBL mean difference (MD) between the groups was −0.053 mm (p = 0.089). There was an estimated decrease of 0.003 in OR (p = 0.284) and an increase of 0.006 mm (p = 0.036) in the MBL MD between groups for every additional month of follow-up. In conclusion, implants placed in fresh extraction sockets present higher risk of failure than implants placed in healed sites. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 5245 KiB

Open AccessArticle

Versatile Strategy for Electrophoretic Deposition of Polyvinylidene Fluoride-Metal Oxide Nanocomposites

by Qinfu Zhao, Xinqian Liu, Stephen Veldhuis and Igor Zhitomirsky

Materials 2021, 14(24), 7902; https://doi.org/10.3390/ma14247902 - 20 Dec 2021

Viewed by 1861

Abstract

Polyvinylidene fluoride (PVDF) is an advanced functional polymer which exhibits excellent chemical and thermal stability, and good mechanical, piezoelectric and ferroelectic properties. This work opens a new strategy for the fabrication of nanocomposites, combining the functional properties of PVDF and advanced inorganic nanomaterials. [...] Read more.

Polyvinylidene fluoride (PVDF) is an advanced functional polymer which exhibits excellent chemical and thermal stability, and good mechanical, piezoelectric and ferroelectic properties. This work opens a new strategy for the fabrication of nanocomposites, combining the functional properties of PVDF and advanced inorganic nanomaterials. Electrophoretic deposition (EPD) has been developed for the fabrication of films containing PVDF and nanoparticles of TiO₂, MnO₂ and NiFe₂O₄. An important finding was the feasibility of EPD of electrically neutral PVDF and inorganic nanoparticles using caffeic acid (CA) and catechol violet (CV) as co-dispersants. The experiments revealed strong adsorption of CA and CV on PVDF and inorganic nanoparticles, which involved different mechanisms and facilitated particle dispersion, charging and deposition. The analysis of the deposition yield data, chemical structure of the dispersants and the microstructure and composition of the films provided an insight into the adsorption and dispersion mechanisms and the influence of deposition conditions on the deposition rate, film microstructure and composition. PVDF films provided the corrosion protection of stainless steel. Overcoming the limitations of other techniques, this investigation demonstrates a conceptually new approach for the fabrication of PVDF-NiFe₂O₄ films, which showed superparamagnetic properties. The approach developed in this investigation offers versatile strategies for the EPD of advanced organic-inorganic nanocomposites. Full article

(This article belongs to the Special Issue Feature Papers for Section Advanced Nanomaterials and Nanotechnology)

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36 pages, 2519 KiB

Open AccessReview

Modification of Glass/Polyester Laminates with Flame Retardants

by Adriana Dowbysz, Mariola Samsonowicz and Bożena Kukfisz

Materials 2021, 14(24), 7901; https://doi.org/10.3390/ma14247901 - 20 Dec 2021

Cited by 12 | Viewed by 3507

Abstract

This paper presents a review of flame retardants used for glass/polyester laminates. It concerns flame retardants withdrawn from use such as compounds containing halogen atoms and flame retardants currently used in the industry, such as inorganic hydroxides, phosphorus and nitrogen-containing compounds, antimony, and [...] Read more.

This paper presents a review of flame retardants used for glass/polyester laminates. It concerns flame retardants withdrawn from use such as compounds containing halogen atoms and flame retardants currently used in the industry, such as inorganic hydroxides, phosphorus and nitrogen-containing compounds, antimony, and boron compounds, as well as tin–zinc compounds. Attention is also drawn to the use of nanoclays and the production of nanocomposites, intumescent flame retardant systems, and mats, as well as polyhedral oligomeric silsesquioxanes. The paper discusses the action mechanism of particular flame retardants and presents their advantages and disadvantages. Full article

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11 pages, 2177 KiB

Open AccessArticle

The Impact of Hydrogenation on Structural and Superconducting Properties of FeTe_0.65Se_0.35 Single Crystals

by Stanislav I. Bondarenko, Anatolij I. Prokhvatilov, Roman Puźniak, Jarosław Piętosa, Andrey A. Prokhorov, Vladimir V. Meleshko, Valeriy P. Timofeev, Valentin P. Koverya, Dariusz Jakub Gawryluk and Andrzej Wiśniewski

Materials 2021, 14(24), 7900; https://doi.org/10.3390/ma14247900 - 20 Dec 2021

Cited by 1 | Viewed by 1543

Abstract

Properties of FeTe_0.65Se_0.35 single crystals, with the onset of critical temperature (T_c^onset) at 15.5 K, were modified via hydrogenation performed for 10–90 h, at temperatures ranging from 20 to 250 °C. It was found that the [...] Read more.

Properties of FeTe_0.65Se_0.35 single crystals, with the onset of critical temperature (T_c^onset) at 15.5 K, were modified via hydrogenation performed for 10–90 h, at temperatures ranging from 20 to 250 °C. It was found that the tetragonal matrix became unstable and crystal symmetry lowered for the samples hydrogenated already at 200 °C. However, matrix symmetry was not changed and the crystal was not destroyed after hydrogenation at 250 °C. Bulk T_c^bulk, determined at the middle of the superconducting transition, which is equal to 12–13 K for the as grown FeTe_0.65Se_0.35, rose by more than 1 K after hydrogenation. The critical current density studied in magnetic field up to 70 kOe increased 4–30 times as a consequence of hydrogenation at 200 °C for 10 h. Electron paramagnetic resonance measurements also showed higher values of T_c^bulk for hydrogenated crystals. Thermal diffusion of hydrogen into the crystals causes significant structural changes, leads to degeneration of crystal quality, and significantly alters superconducting properties. After hydrogenation, a strong correlation was noticed between the structural changes and changes in the parameters characterizing the superconducting state. Full article

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21 pages, 7693 KiB

Open AccessArticle

Influence of Forced Carbonisation on the Binding Properties of Sludge with a High β-Belite Content

by Aleksandr Bakhtin, Nikolay Lyubomirskiy, Stanisław Fic and Tamara Bakhtina

Materials 2021, 14(24), 7899; https://doi.org/10.3390/ma14247899 - 20 Dec 2021

Cited by 5 | Viewed by 1786

Abstract

Alternative binders activated by forced carbonisation are regarded as one of the potential solutions to reducing greenhouse gas emissions, water, and energy consumption. Such binders, in particular those based on nepheline sludge (a by-product of alumina production), cured in carbon dioxide with subsequent [...] Read more.

Alternative binders activated by forced carbonisation are regarded as one of the potential solutions to reducing greenhouse gas emissions, water, and energy consumption. Such binders, in particular those based on nepheline sludge (a by-product of alumina production), cured in carbon dioxide with subsequent hydration, are clinkerless building materials. The development of such binders contributes to the involvement of multi-tonnage solid industrial waste in the production cycle. This type of waste is capable of binding man-made CO₂ and transforming it into stable insoluble compounds, having binder properties. The optimum technological parameters of the forced carbonisation of the nepheline slime binder was determined by the mathematical planning of the experiment. The novelty of the research is the expansion of the secondary raw material base that can bind the man-made CO₂ with obtaining the construction products of appropriate quality. It was revealed that the process of active CO₂ absorption by the minerals of nepheline slime is observed in the first 120 min of the forced carbonization. Immediately after carbonisation, the resulting material develops compressive strength up to 57.64 MPa, and at the subsequent hydration within 28 days this figure increases to 68.71 MPa. Calcium carbonate is the main binder that determines the high mechanical properties of the samples. During the subsequent hydration of the uncoated belite, gel-like products are formed, which additionally harden the carbonised matrix. Thus, after the forced carbonisation and the following 28 days of hardening, the material with compressive strength in the range 4.38–68.71 MPa and flexural strength of 3.1–8.9 MPa was obtained. This material was characterised by water absorption by mass in the range of 13.9–23.3% and the average density of 1640–1886 kg/m³. The softening coefficient of the material was 0.51–0.99. The results obtained enables one to consider further prospects for research in this area, in terms of the introduction of additional technological parameters to study the process of forced carbonisation of nepheline slime. Full article

(This article belongs to the Special Issue Durability and Surface Protection of Porous Materials and External Building Partitions)

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21 pages, 6041 KiB

Open AccessArticle

Effects of Temperature on the Evolution of Yield Surface and Stress Asymmetry in A356–T7 Cast Aluminium Alloy

by Elanghovan Natesan, Johan Ahlström, Stefan Eriksson and Christer Persson

Materials 2021, 14(24), 7898; https://doi.org/10.3390/ma14247898 - 20 Dec 2021

Cited by 6 | Viewed by 2364

Abstract

As the electrification of vehicle powertrains takes prominence to meet stringent emission norms, parts of internal combustion engines like cylinder heads are subjected to an increased number of thermal load cycles. The cost-effective design of such structures subjected to cyclic thermo-mechanical loads relies [...] Read more.

As the electrification of vehicle powertrains takes prominence to meet stringent emission norms, parts of internal combustion engines like cylinder heads are subjected to an increased number of thermal load cycles. The cost-effective design of such structures subjected to cyclic thermo-mechanical loads relies on the development of accurate material models capable of describing the continuum deformation behaviour of the material. This study investigates the effect of temperature on the evolution of flow stress under cyclic loading in A356-T7 + 0.5% Cu cast aluminium alloy commonly used in modern internal combustion engine cylinder heads. The material exhibits peak stress and flow stress asymmetry with the stress response and flow stress of the material under compressive loading higher than under tension. This peak and flow stress asymmetry decrease with an increase in temperature. To compare this stress asymmetry against conventional steel, cyclic strain-controlled fatigue tests are run on fully pearlitic R260 railway steel material. To study the effect of mean strain on the cyclic mean stress evolution and fatigue behaviour of the alloy, tests with tensile and compressive mean strains of +0.2% and −0.2% are compared against fully reversed (R_ε = −1) strain-controlled tests. The material exhibits greater stress asymmetry between the peak tensile and peak compressive stresses for the strain-controlled tests with a compressive mean strain than the tests with an identical magnitude tensile mean strain. The material exhibits mean stress relaxation at all temperatures. Reduced durability of the material is observed for the tests with tensile mean strains at lower test temperatures of up to 150 °C. The tensile mean strains at elevated temperatures do not exhibit such a detrimental effect on the endurance limit of the material. Full article

(This article belongs to the Special Issue Mechanical Properties and Characterization of Metallic Materials for Lightweight Structures)

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24 pages, 196458 KiB

Open AccessArticle

Prediction of Material Failure Time for a Bucket Wheel Excavator Boom Using Computer Simulation

by Andrei Andraș, Sorin Mihai Radu, Ildiko Brînaș, Florin Dumitru Popescu, Daniela Ioana Budilică and Eva Biro Korozsi

Materials 2021, 14(24), 7897; https://doi.org/10.3390/ma14247897 - 20 Dec 2021

Cited by 10 | Viewed by 3286

Abstract

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA [...] Read more.

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA or other techniques being implemented in the recent years. In this paper a fatigue study is conducted on the boom of a BWE. Based on a computer model of the boom previously developed in SOLIDWORKS by our author team, first the modal analysis is conducted for three positions of the boom by studying the frequency response during the excavation process. This is followed by the time response determination corresponding to the maximum displacement frequency, in order to assess the stress during the excavation process, which causes the material fatigue in the boom structure. It was found that the maximum displacements appear when the BWE boom operates in a horizontal position. The aim was to estimate the period of time to failure in order to prevent unwanted accidents, and to develop a method that is applicable to any surface mining or industrial machine with similar structure. Full article

(This article belongs to the Special Issue Advances in Structural Analysis of Materials: Finite Element Modeling)

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15 pages, 1257 KiB

Open AccessArticle

Precise-Integration Time-Domain Formulation for Optical Periodic Media

by Joan Josep Sirvent-Verdú, Jorge Francés, Andrés Márquez, Cristian Neipp, Mariela Álvarez, Daniel Puerto, Sergi Gallego and Inmaculada Pascual

Materials 2021, 14(24), 7896; https://doi.org/10.3390/ma14247896 - 20 Dec 2021

Cited by 1 | Viewed by 1825

Abstract

A numerical formulation based on the precise-integration time-domain (PITD) method for simulating periodic media is extended for overcoming the Courant-Friedrich-Levy (CFL) limit on the time-step size in a finite-difference time-domain (FDTD) simulation. In this new method, the periodic boundary conditions are implemented, permitting [...] Read more.

A numerical formulation based on the precise-integration time-domain (PITD) method for simulating periodic media is extended for overcoming the Courant-Friedrich-Levy (CFL) limit on the time-step size in a finite-difference time-domain (FDTD) simulation. In this new method, the periodic boundary conditions are implemented, permitting the simulation of a wide range of periodic optical media, i.e., gratings, or thin-film filters. Furthermore, the complete tensorial derivation for the permittivity also allows simulating anisotropic periodic media. Numerical results demonstrate that PITD is reliable and even considering anisotropic media can be competitive compared to traditional FDTD solutions. Furthermore, the maximum allowable time-step size has been demonstrated to be much larger than that of the CFL limit of the FDTD method, being a valuable tool in cases in which the steady-state requires a large number of time-steps. Full article

(This article belongs to the Special Issue New Advances in Modeling, Simulation and Analysis of Optical Materials)

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15 pages, 6495 KiB

Open AccessArticle

Microstructure and Defect-Based Fatigue Mechanism Evaluation of Brazed Coaxial Ti/Al₂O₃ Joints for Enhanced Endoprosthesis Design

by Johannes L. Otto, Ivan Fedotov, Milena Penyaz, Thorge Schaum, Anke Kalenborn, Boris Kalin, Oleg Sevryukov and Frank Walther

Materials 2021, 14(24), 7895; https://doi.org/10.3390/ma14247895 - 20 Dec 2021

Viewed by 2116

Abstract

Alumina-based ceramic hip endoprosthesis heads have excellent tribological properties, such as low wear rates. However, stress peaks can occur at the point of contact with the prosthesis stem, increasing the probability of fracture. This risk should be minimized, especially for younger and active [...] Read more.

Alumina-based ceramic hip endoprosthesis heads have excellent tribological properties, such as low wear rates. However, stress peaks can occur at the point of contact with the prosthesis stem, increasing the probability of fracture. This risk should be minimized, especially for younger and active patients. Metal elevations at the stem taper after revision surgery without removal of a well-fixed stem are also known to increase the risk of fracture. A solution that also eliminates the need for an adapter sleeve could be a fixed titanium insert in the ceramic ball head, which would be suitable as a damping element to reduce the occurrence of stress peaks. A viable method for producing such a permanent titanium–ceramic joint is brazing. Therefore, a brazing method was developed for coaxial samples, and two modifications were made to the ceramic surface to braze a joint that could withstand high cyclic loading. This cyclic loading was applied in multiple amplitude tests in a self-developed test setup, followed by fractographic studies. Computed tomography and microstructural analyses—such as energy dispersive X-ray spectroscopy—were also used to characterize the process–structure–property relationships. It was found that the cyclic loading capacity can be significantly increased by modification of the surface structure of the ceramic. Full article

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18 pages, 4394 KiB

Open AccessArticle

Chemical Modification of Chitosan for Removal of Pb(II) Ions from Aqueous Solutions

by Adriana Popa, Aurelia Visa, Bianca Maranescu, Iosif Hulka and Lavinia Lupa

Materials 2021, 14(24), 7894; https://doi.org/10.3390/ma14247894 - 20 Dec 2021

Cited by 10 | Viewed by 2073

Abstract

Biomacromolecule have a significant contribution to the adsorption of metal ions. Moreover, chitosan is one of the most studied biomacromolecule, which has shown a good performance in the field of wastewater treatment. In this context, a new adsorbent of the aminophosphonic modified chitosan-supported [...] Read more.

Biomacromolecule have a significant contribution to the adsorption of metal ions. Moreover, chitosan is one of the most studied biomacromolecule, which has shown a good performance in the field of wastewater treatment. In this context, a new adsorbent of the aminophosphonic modified chitosan-supported Ni(II) ions type was prepared from the naturally biopolymer, chitosan. In the first step, modified chitosan with aminophosphonic acid groups was prepared using the “one-pot” Kabachnik-Fields reaction. It was characterized by different techniques: FTIR, SEM/EDAX, TGA, and ³¹P-NMR. In the second step, the modified chitosan with aminophosphonic acid was impregnated with Ni(II) ions using the hydrothermal reaction at different values of pH (5, 6 and 7). The physical-chemical characteristics of final products (modified chitosan carrying aminophosphonic groups and Ni(II) ions) were investigated using FTIR, SEM images, EDAX spectra and thermogravimetric analysis. In this work, the most important objective was the investigation of the adsorbent performance of the chitosan modified with aminophosphonic groups and Ni(II) ions in the process of removing Pb(II) ions from aqueous solutions by studying the effect of pH, contact time, and Pb(II) ions concentration. For removal of Pb(II) ions from the aqueous solution, the batch adsorption method was used. Full article

(This article belongs to the Special Issue Novel Polymeric Materials for High-Performance and Biomedical Applications)

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13 pages, 5373 KiB

Open AccessArticle

Green Synthesis of Silver-Decorated Magnetic Particles for Efficient and Reusable Antimicrobial Activity

by Sachin V. Otari, Vipin Chandra Kalia, Aarti Bisht, In-Won Kim and Jung-Kul Lee

Materials 2021, 14(24), 7893; https://doi.org/10.3390/ma14247893 - 20 Dec 2021

Cited by 5 | Viewed by 1797

Abstract

Metal and metal hybrid nanostructures have shown tremendous application in the biomedical and catalytic fields because of their plasmonic and catalytic properties. Here, a green and clean method was employed for the synthesis of silver nanoparticle (Ag NP)-SiO₂-Fe₂O₃ [...] Read more.

Metal and metal hybrid nanostructures have shown tremendous application in the biomedical and catalytic fields because of their plasmonic and catalytic properties. Here, a green and clean method was employed for the synthesis of silver nanoparticle (Ag NP)-SiO₂-Fe₂O₃ hybrid microstructures, and biomolecules from green tea extracts were used for constructing the hybrid structures. The SiO₂-Fe₂O₃ structures were synthesized using an ethanolic green tea leaf extract to form Bio-SiO₂-Fe₂O₃ (BSiO₂-Fe₂O₃) structures. Biochemical studies demonstrated the presence of green tea biomolecules in the BSiO₂ layer. Reduction of the silver ions was performed by a BSiO₂ layer to form Ag NPs of 5–10 nm in diameter in and on the BSiO₂-Fe₂O₃ microstructure. The reduction process was observed within 600 s, which is faster than that reported elsewhere. The antimicrobial activity of the Ag-BSiO₂-Fe₂O₃ hybrid structure was demonstrated against Staphylococcus aureus and Escherichia coli, and the nanostructures were further visualized using confocal laser scanning microscopy (CLSM). The magnetic properties of the Ag-BSiO₂-Fe₂O₃ hybrid structure were used for studying reusable antimicrobial activity. Thus, in this study, we provide a novel green route for the construction of a biomolecule-entrapped SiO₂-Fe₂O₃ structure and their use for the ultra-fast formation of Ag NPs to form antimicrobial active multifunctional hybrid structures. Full article

(This article belongs to the Special Issue Functional Materials for Therapeutic and Industrial Applications)

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12 pages, 2310 KiB

Open AccessArticle

Quantification of Chlorides and Sulphates on Concrete Surfaces Using Portable X-ray Fluorescence. Optimization of the Measurement Method Using Monte Carlo Simulation

by Servando Chinchón-Payá, Julio E. Torres Martín, Antonio Silva Toledo and Javier Sánchez Montero

Materials 2021, 14(24), 7892; https://doi.org/10.3390/ma14247892 - 20 Dec 2021

Cited by 6 | Viewed by 1799

Abstract

A correct assessment of the pathologies that can affect a reinforced concrete structure is required in order to define the repair procedure. This work addresses the challenge of quantifying chlorides and sulphates directly on the surface of concrete. The quantification was carried out [...] Read more.

A correct assessment of the pathologies that can affect a reinforced concrete structure is required in order to define the repair procedure. This work addresses the challenge of quantifying chlorides and sulphates directly on the surface of concrete. The quantification was carried out by means of X-ray fluorescence analysis on the surface of concrete specimens at different points with portable equipment. Concrete prisms were made with different amounts of NaCl and Na₂SO₄. To avoid the influence of coarse aggregate, a qualitative estimate of the amount of coarse aggregate analyzed has been made, although the results show that there is no significant influence. Monte Carlo simulations were carried out in order to establish the necessary number of random analyses of the mean value to be within an acceptable range of error. In the case of quantifying sulphates, it is necessary to carry out six random analyses on the surface, and eight measurements in the case of quantifying chlorides; in this way, it is ensured that errors are below 10% in 95% of the cases. The results of the study highlight that a portable XRF device can be used in situ to obtain concentrations of chlorides and sulphates of a concrete surface with good accuracy. There is no need to take samples and bring them to a laboratory, allowing lower overall costs in inspection and reparation works. Full article

(This article belongs to the Special Issue Durability and Safety of Concrete Structures)

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19 pages, 7216 KiB

Open AccessArticle

Assessing the Asphalt Binder Film Thickness in Recycled Asphalt Mixtures Using Micro-Level Techniques

by Fazli Karim and Jawad Hussain

Materials 2021, 14(24), 7891; https://doi.org/10.3390/ma14247891 - 20 Dec 2021

Cited by 5 | Viewed by 2134

Abstract

Adequate asphalt binder film thickness (ABFT) delivers skeletal integrity in recycled asphalt mixtures, resulting in long-lasting roadways when exposed to traffic and environment. The inaccurate measurement of ABFT and the consequences of not having adequate film thickness model has substantially introduced discrepancies in [...] Read more.

Adequate asphalt binder film thickness (ABFT) delivers skeletal integrity in recycled asphalt mixtures, resulting in long-lasting roadways when exposed to traffic and environment. The inaccurate measurement of ABFT and the consequences of not having adequate film thickness model has substantially introduced discrepancies in predicting actual performance of recycled asphalt mixtures. Expansion of the ultra-modern expertise and SuperPave requirements necessitate the revision of authentic ABFT at micro-level. The current study identifies the weaknesses of the current methods of estimating ABFT and provides results that are reliable and useful, using modern measurement methods. Using scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS), this study measures the ABFT around the tiniest particle of 0.2 μm magnitude, entrenched in asphalt mastic in recycled asphalt mixtures. The ABFT, obtained through image analysis, is compared with those obtained through available analytical models. The study utilizes different asphalt mixtures, containing varying proportions of recycled asphalt mixture and rejuvenators. The aggregate, virgin, and recycled binders were characterized in terms of physical and rheological properties, respectively. Marshall mix design was carried out for the conventional and recycled mixture, containing 40%, 50%, and 60% recycled materials, rejuvenated with 3%, 6%, 9%, and 12% waste engine oil (WEO) at a mixing temperature of 160 °C, based on viscosity of the virgin and rejuvenated binder. ABFT was assessed through analytical models and image analysis for the aforesaid recycled asphalt mixtures, prepared at optimum binder and rejuvenator content as per protocol outlined in ASTM D1559. The analytical estimation of ABFT, in the aforesaid recycled asphalt mixtures, revealed that the ABFT fluctuates from 6.4 μm to 13.7 microns, with a significant association to recycled asphalt mixture and rejuvenator content. However, the image analysis revealed that the ABFT, in the aforesaid recycled asphalt mixtures, fluctuates from 0.4 μm to 2 microns, without any association to recycled asphalt mixture or rejuvenator content. The image analysis indicated that the recycled asphalt mixtures typically comprise of mortar, happening in uneven shape, and are used to grip large aggregates. The asphalt mastic, a blend of bitumen and mineral filler, was found to be an interlocking agent, used to grasp only fine particles in asphalt mortar. The asphalt binder film was discovered to be a deviating stand-alone entity that only exists around the mineral fillers in the asphalt mastic as a non-absorbed binder, occupying an imprecise space of 0.4 μm to 2 microns, among the filler particles. The current findings will be useful to design asphalt pavements through the aforesaid precise limit of SEM-based ABFT rather than traditionally measured ABFT to predict the actual performance of recycled asphalt mixtures. Full article

(This article belongs to the Special Issue Asphalt Mixtures with Reclaimed Asphalt Pavement)

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17 pages, 746 KiB

Open AccessEditor’s ChoiceArticle

Effect of Inhomogeneous Broadening in Ultraviolet III-Nitride Light-Emitting Diodes

by Friedhard Römer, Martin Guttmann, Tim Wernicke, Michael Kneissl and Bernd Witzigmann

Materials 2021, 14(24), 7890; https://doi.org/10.3390/ma14247890 - 20 Dec 2021

Cited by 13 | Viewed by 2018

Abstract

In the past years, light-emitting diodes (LED) made of GaN and its related ternary compounds with indium and aluminium have become an enabling technology in all areas of lighting. Visible LEDs have yet matured, but research on deep ultraviolet (UV) LEDs is still [...] Read more.

In the past years, light-emitting diodes (LED) made of GaN and its related ternary compounds with indium and aluminium have become an enabling technology in all areas of lighting. Visible LEDs have yet matured, but research on deep ultraviolet (UV) LEDs is still in progress. The polarisation in the anisotropic wurtzite lattice and the low free hole density in p-doped III-nitride compounds with high aluminium content make the design for high efficiency a critical step. The growth kinetics of the rather thin active quantum wells in III-nitride LEDs makes them prone to inhomogeneous broadening (IHB). Physical modelling of the active region of III-nitride LEDs supports the optimisation by revealing the opaque active region physics. In this work, we analyse the impact of the IHB on the luminescence and carrier transport III-nitride LEDs with multi-quantum well (MQW) active regions by numerical simulations comparing them to experimental results. The IHB is modelled with a statistical model that enables efficient and deterministic simulations. We analyse how the lumped electronic characteristics including the quantum efficiency and the diode ideality factor are related to the IHB and discuss how they can be used in the optimisation process. Full article

(This article belongs to the Special Issue Advances in Light-Emitting Structures and Materials)

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14 pages, 7378 KiB

Open AccessArticle

Enhanced Hydrogen Generation Performance of Al-Rich Alloys by a Melting-Mechanical Crushing-Ball Milling Method

by Lixiang Zhu, Meishuai Zou, Xiaodong Zhang, Lichen Zhang, Xiaoxuan Wang, Tinglu Song, Shuo Wang and Xiaodong Li

Materials 2021, 14(24), 7889; https://doi.org/10.3390/ma14247889 - 20 Dec 2021

Cited by 17 | Viewed by 2281

Abstract

The main problem for the application of hydrogen generated via hydrolysis of metal alloys is the low hydrogen generation rate (HGR). In this paper, active Al alloys were prepared using a new coupled method-melting-mechanical crushing-mechanical ball milling method to enhance the HGR at [...] Read more.

The main problem for the application of hydrogen generated via hydrolysis of metal alloys is the low hydrogen generation rate (HGR). In this paper, active Al alloys were prepared using a new coupled method-melting-mechanical crushing-mechanical ball milling method to enhance the HGR at room temperature. This method contains three steps, including the melting of Al, Ga, In, and Sn ingots with low melting alloy blocks and casting into plates, then crushing alloy plate into powders and ball milling with chloride salts such as NiCl₂ and CoCl₂ were added during the ball milling process. The microstructure and phase compositions of Al alloys and reaction products were investigated via X-ray diffraction and scanning electron microscopy with energy dispersed X-ray spectroscopy. The low-melting-point Ga-In -Sn (GIS) phases contain a large amount of Al can act as a transmission medium for Al, which improves the diffusion of Al to Al/H₂O reaction sites. Finer GIS phases after ball milling can further enhance the diffusion of Al and thus enhance the activity of Al alloy. The hydrogen generation performance through hydrolysis of water with Al at room temperature was investigated. The results show that the H₂ generation performance of the Al-low-melting point alloy composite powder is significantly higher than the results reported to date. The highest H₂ generation rate and H₂ conversion efficiency can reach 5337 mL·min⁻¹·g⁻¹ for the hydrolysis of water with 1 g active alloy. Full article

(This article belongs to the Topic Metallurgical and Materials Engineering)

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21 pages, 9650 KiB

Open AccessArticle

Active Control of Stiffness of Tensegrity Plate-like Structures Built with Simplex Modules

by Paulina Obara and Justyna Tomasik

Materials 2021, 14(24), 7888; https://doi.org/10.3390/ma14247888 - 20 Dec 2021

Cited by 5 | Viewed by 1802

Abstract

The aim of this study is to prove that it is possible to control the static behavior of tensegrity plate-like structures. This possibility is very important, particularly in the case of deployable structures. Here, we analyze the impact the support conditions of the [...] Read more.

The aim of this study is to prove that it is possible to control the static behavior of tensegrity plate-like structures. This possibility is very important, particularly in the case of deployable structures. Here, we analyze the impact the support conditions of the structure have on the existence of specific characteristics, such as self-stress states and infinitesimal mechanisms, and, consequently, on the active control. Plates built with Simplex modules are considered. Firstly, the presence of the specific characteristics is examined, and a classification is carried out. Next, the influence of the level of self-stress state on the behavior of structures is analyzed. A geometrically non-linear model, implemented in an original program, written in the Mathematica environment, is used. The results confirm the feasibility of the active control of stiffness of tensegrity plate-like structures characterized by the presence of infinitesimal mechanisms. In the case when mechanisms do not exist, structures are insensitive to the initial prestress level. It is possible to control the occurrence of mechanisms by changing the support conditions of the structure. Based on the obtained results, tensegrity is very promising structural concept, applicable in many areas, when conventional solutions are insufficient. Full article

(This article belongs to the Special Issue Modeling and Analysis of Static, Dynamic, and Thermal Behavior of Shell, Plate, and Beam Structures)

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17 pages, 3215 KiB

Open AccessArticle

Structure Prediction and Mechanical Properties of Silicon Hexaboride on Ab Initio Level

by Tamara Škundrić, Branko Matović, Aleksandra Zarubica, Jelena Zagorac, Peter Tatarko and Dejan Zagorac

Materials 2021, 14(24), 7887; https://doi.org/10.3390/ma14247887 - 20 Dec 2021

Cited by 8 | Viewed by 2064

Abstract

Silicon borides represent very appealing industrial materials for research owing to their remarkable features, and, together with other boride and carbide-based materials, have very wide applications. Various Si–B phases have been investigated in the past, however a limited number of studies have been [...] Read more.

Silicon borides represent very appealing industrial materials for research owing to their remarkable features, and, together with other boride and carbide-based materials, have very wide applications. Various Si–B phases have been investigated in the past, however a limited number of studies have been done on the pristine SiB₆ compound. Structure prediction using a data mining ab initio approach has been performed in pure silicon hexaboride. Several novel structures, for which there are no previous experimental or theoretical data, have been discovered. Each of the structure candidates were locally optimized on the DFT level, employing the LDA-PZ and the GGA-PBE functional. Mechanical and elastic properties for each of the predicted and experimentally observed modifications have been investigated in great detail. In particular, the ductility/brittleness relationship, the character of the bonding, Young’s modulus E, bulk modulus B, and shear modulus K, including anisotropy, have been calculated and analyzed. Full article

(This article belongs to the Special Issue Feature Paper Collection of Topical Advisory Members)

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12 pages, 2460 KiB

Open AccessArticle

Zirconia vs. Titanium Dental Implants: Primary Stability In-Vitro Analysis

by Nerea Arlucea, Aritza Brizuela-Velasco, Markel Dieguez-Pereira, Miquel Punset, Meritxell Molmeneu, Fernando Sánchez Lasheras, Hector deLlanos-Lanchares and Ángel Álvarez-Arenal

Materials 2021, 14(24), 7886; https://doi.org/10.3390/ma14247886 - 20 Dec 2021

Cited by 6 | Viewed by 2376

Abstract

The present experimental trial uses two types of dental implants, one made of titanium (Ti₆A_l4V) and the other one of zirconia (ZrO₂), but both of identical design, to compare their stability and micro-movements values under load. One [...] Read more.

The present experimental trial uses two types of dental implants, one made of titanium (Ti₆A_l4V) and the other one of zirconia (ZrO₂), but both of identical design, to compare their stability and micro-movements values under load. One of each type of implant (n = 42) was placed into 21 cow ribs, recording the insertion torque and the resonance frequency using a specific transducer. Subsequently, a prosthetic crown made of PMMA was screwed onto each of the implants in the sample. They were then subjected to a static compression load on the vestibular cusp of the crown. The resulting micromovements were measured. The zirconia implants obtained a higher mean of both IT and RFA when compared with those of titanium, with statistically significant differences in both cases (p = 0.0483 and p = 0.0296). However, the micromovement values when load was applied were very similar for both types, with the differences between them (p = 0.3867) not found to be statistically significant. The results show that zirconia implants have higher implant stability values than titanium implants. However, the fact that there are no differences in micromobility values implies that caution should be exercised when applying clinical protocols for zirconia based on RFA, which only has evidence for titanium. Full article

(This article belongs to the Special Issue Ti Alloys for Dental Implant Applications-Series II)

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13 pages, 2024 KiB

Open AccessArticle

Synthesis of Arylene Ether-Type Hyperbranched Poly(triphenylamine) for Lithium Battery Cathodes

by Inah Kang, Taewoong Lee, Young Rok Yoon, Jee Woo Kim, Byung-Kwon Kim, Jinhee Lee, Jin Hong Lee and Sang Youl Kim

Materials 2021, 14(24), 7885; https://doi.org/10.3390/ma14247885 - 20 Dec 2021

Cited by 1 | Viewed by 2728

Abstract

We synthesized a new poly(triphenylamine), having a hyperbranched structure, and employed it in lithium-ion batteries as an organic cathode material. Two types of monomers were prepared with hydroxyl groups and nitro leaving groups, activated by a trifluoromethyl substituent, and then polymerized via the [...] Read more.

We synthesized a new poly(triphenylamine), having a hyperbranched structure, and employed it in lithium-ion batteries as an organic cathode material. Two types of monomers were prepared with hydroxyl groups and nitro leaving groups, activated by a trifluoromethyl substituent, and then polymerized via the nucleophilic aromatic substitution reaction. The reactivity of the monomers differed depending on the number of hydroxyl groups and the A₂B type monomer with one hydroxyl group successfully produced poly(triphenylamine). Based on thermal, optical, and electrochemical analyses, a composite poly(triphenylamine) electrode was made. The electrochemical performance investigations confirmed that the lithium-ion batteries, fabricated with the poly(triphenylamine)-based cathodes, had reasonable specific capacity values and stable cycling performance, suggesting the potential of this hyperbranched polymer in cathode materials for lithium-ion batteries. Full article

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16 pages, 3505 KiB

Open AccessArticle

XAS Data Preprocessing of Nanocatalysts for Machine Learning Applications

by Oleg O. Kartashov, Andrey V. Chernov, Dmitry S. Polyanichenko and Maria A. Butakova

Materials 2021, 14(24), 7884; https://doi.org/10.3390/ma14247884 - 20 Dec 2021

Cited by 10 | Viewed by 3778

Abstract

Innovative development in the energy and chemical industries is mainly dependent on advances in the accelerated design and development of new functional materials. The success of research in new nanocatalysts mainly relies on modern techniques and approaches for their precise characterization. The existing [...] Read more.

Innovative development in the energy and chemical industries is mainly dependent on advances in the accelerated design and development of new functional materials. The success of research in new nanocatalysts mainly relies on modern techniques and approaches for their precise characterization. The existing methods of experimental characterization of nanocatalysts, which make it possible to assess the possibility of using these materials in specific chemical reactions or applications, generate significant amounts of heterogeneous data. The acceleration of new functional materials, including nanocatalysts, directly depends on the speed and quality of extracting hidden dependencies and knowledge from the obtained experimental data. Usually, such experiments involve different characterization techniques and different types of X-ray absorption spectroscopy (XAS) too. Using the machine learning (ML) methods based on XAS data, we can study and predict the atomic-scale structure and another bunch of parameters for the nanocatalyst efficiently. However, before using any ML model, it is necessary to make sure that the XAS raw experimental data is properly pre-processed, cleared, and prepared for ML application. Usually, the XAS preprocessing stage is vaguely presented in scientific studies, and the main efforts of researchers are devoted to the ML description and implementation stage. However, the quality of the input data influences the quality of ML analysis and the prediction results used in the future. This paper fills the gap between the stage of obtaining XAS data from synchrotron facilities and the stage of using and customizing various ML analysis and prediction models. We aimed this study to develop automated tools for the preprocessing and presentation of data from physical experiments and the creation of deposited datasets on the basis of the example of studying palladium-based nanocatalysts using synchrotron radiation facilities. During the study, methods of preliminary processing of XAS data were considered, which can be conditionally divided into X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). This paper proposes a software toolkit that implements data preprocessing scenarios in the form of a single pipeline. The main preprocessing methods used in this study proposed are principal component analysis (PCA); z-score normalization; the interquartile method for eliminating outliers in the data; as well as the k-means machine learning method, which makes it possible to clarify the phase of the studied material sample by clustering feature vectors of experiments. Among the results of this study, one should also highlight the obtained deposited datasets of physical experiments on palladium-based nanocatalysts using synchrotron radiation. This will allow for further high-quality data mining to extract new knowledge about materials using artificial intelligence methods and machine learning models, and will ensure the smooth dissemination of these datasets to researchers and their reuse. Full article

(This article belongs to the Special Issue Functional Materials, Machine Learning, and Optimization)

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