-
Materials (Basel, Switzerland) Jun 2024Increasing demand for electrical and electronic equipment results in the generation of a rapidly growing waste stream, known by the acronym WEEE (waste electrical and...
Increasing demand for electrical and electronic equipment results in the generation of a rapidly growing waste stream, known by the acronym WEEE (waste electrical and electronic equipment). The purpose of this study was to evaluate the effectiveness of green sink-float treatment in sorting plastic polymers typically found in WEEE (PP, ABS, PA6, PS, and PVC). Molasses, a by-product of sugar bio-refining, was added in various concentrations to water to form solutions at different densities. The methodology was initially tested on virgin polymers; later, it was applied to plastics from a WEEE treatment plant. The polymers were characterised through near infrared spectroscopy (NIRS) and Fourier-transform infrared spectroscopy (FTIRS) analyses; the detection of any additives and flame retardants was conducted using the sliding spark technology (SSS2) and scanning electron microscope (SEM-EDX). The results showed that, for plastics from WEEE, the recovery efficiency was 55.85% for PP in a solution of tap water while the remaining part of PP (44.15%) was recovered in a solution of water to which 90% molasses was added. Furthermore, 100% recovery efficiency was obtained for PS and 93.73% for ABS in a solution of tap water with the addition of 10% / molasses. A recovery efficiency of 100% was obtained for PVC and 100% for PA6 in a solution consisting solely of molasses.
PubMed: 38930409
DOI: 10.3390/ma17123041 -
An Experimental Study on the Frictional Behavior of Ultrathin Metal Sheets at Elevated Temperatures.Materials (Basel, Switzerland) Jun 2024Hot forming is an effective approach for improving the formability of ultrathin metal sheets, such as those made of stainless steel and pure titanium. However, the...
Hot forming is an effective approach for improving the formability of ultrathin metal sheets, such as those made of stainless steel and pure titanium. However, the increased friction coefficient between the tool and the high-temperature metal sheet negatively affects material flow during hot forming, potentially resulting in severe local thinning or even cracking. This study explores the frictional behavior of 0.1 mm thick ferritic stainless steel (FSS) and commercially pure titanium (CP-Ti) sheets at elevated temperatures. A friction testing apparatus was developed to measure the friction coefficients of these metal sheets from room temperature (25 °C) up to 600 °C. The friction coefficient of the FSS sheet increased monotonically with temperature, whereas that of the CP-Ti sheet first increased and then decreased. Post-friction testing microscopic examination demonstrated that built-up edges formed on the surfaces of the friction blocks when rubbed against the stainless steel, contributing to the higher friction coefficients. This study provides a foundation for understanding frictional behavior during the hot forming of ultrathin metal sheets.
PubMed: 38930378
DOI: 10.3390/ma17123009 -
Materials (Basel, Switzerland) Jun 2024As a renewable, environmentally friendly, natural, and organic material, wood has been receiving extensive attention from various industries. However, the hydrophilicity...
As a renewable, environmentally friendly, natural, and organic material, wood has been receiving extensive attention from various industries. However, the hydrophilicity of wood significantly impacts the stability and durability of its products, which can be effectively addressed by constructing superhydrophobic coatings on the surface of wood. In this study, tung oil, carnauba wax, and silica nanoparticles were used to construct superhydrophobic coatings on hydrophilic wood surfaces by a facile two-step dip-coating method. The surface wettability and morphology of the coatings were analyzed by a contact angle meter and scanning electron microscope, respectively. The results suggest that the coating has a micron-nanosized two-tiered structure, and the contact angle of the coating is higher than 150° and the roll-off angle is lower than 10°. Sandpaper abrasion tests and UV diffuse reflectance spectra indicate that the coatings have excellent abrasion resistance and good transparency. In addition, the coated wood shows excellent self-cleaning and water resistance, which have great potential for applications in industry and furniture manufacturing.
PubMed: 38930369
DOI: 10.3390/ma17123000 -
Materials (Basel, Switzerland) Jun 2024As the reliability and lifespan requirements of modern equipment continues to escalate, the problems with very high cycle fatigue (VHCF) has obtained increasingly... (Review)
Review
As the reliability and lifespan requirements of modern equipment continues to escalate, the problems with very high cycle fatigue (VHCF) has obtained increasingly widespread attention, becoming a hot topic in fatigue research. Titanium alloys, which are the most extensively used metal materials in the modern aerospace industry, are particularly prone to VHCF issues. The present study systematically reviewed and summarized the latest (since 2010) developments in VHCF research on titanium alloy, with special focus on the (i) experimental methods, (ii) macroscopic and microscopic characteristics of the fatigue fractures, and (iii) construction of fatigue fracture models. More specifically, the review addresses the technological approaches that were used, mechanisms of fatigue crack initiation, features of the S-N curves and Goodman diagrams, and impact of various factors (such as processing, temperature, and corrosion). In addition, it elucidates the damage mechanisms, evolution, and modeling of VHCF in titanium alloys, thereby improving the understanding of VHCF patterns in titanium alloys and highlighting the current challenges in VHCF research.
PubMed: 38930356
DOI: 10.3390/ma17122987 -
Materials (Basel, Switzerland) Jun 2024A ZrB-copper-graphite composite was produced through powder metallurgy and was tested as a new electric brush material. The aim of this paper was to study the effect of...
A ZrB-copper-graphite composite was produced through powder metallurgy and was tested as a new electric brush material. The aim of this paper was to study the effect of ZrB addition on the composite's properties. Besides its physical properties such as density and resistivity, its mechanical properties, such as hardness, bending strength and wear resistance, were studied. A scanning electron microscope (SEM) was used to study the morphology of the wear surface, and a configured energy-dispersive spectrometer (EDS) was used to research the chemical composition of the samples. The results showed that, with the addition of ZrB, the composite's properties such as density, resistivity, hardness, and bending strength improved significantly. Compared with samples without ZrB, samples with the addition of 4% ZrB achieved a hardness of 87.5 HRA, which was improved by 45.8%, and a bending strength of 53.1 MPa, which was increased by nearly 50.0%. Composites with 1% content of ZrB showed the best wear resistance under non-conductive friction; however, under conductive friction, composites with 4% content of ZrB showed better wear resistance.
PubMed: 38930349
DOI: 10.3390/ma17122980 -
Materials (Basel, Switzerland) Jun 2024As an emerging repair method, the enzyme-induced calcium carbonate precipitation (EICP) technique has the advantages of being highly economical, eco-friendly, and...
As an emerging repair method, the enzyme-induced calcium carbonate precipitation (EICP) technique has the advantages of being highly economical, eco-friendly, and durable. The optimal repair conditions were obtained by taking cement mortar as the research object, adding two types of filling medium, using three EICP-based repair methods to repair the cement mortar with different crack widths, and combining ultrasonic testing and strength testing to evaluate the mechanical properties and repair effects of the repair mortar. The microscopic structure of the mortar was established using mesoscopic and microscopic tests (XRD, SEM, and EDS), thereby revealing the mechanism of repair based on EICP. The test results show that, when quartz sand is used as the repair medium, more calcium carbonate adheres to the cross-section of test samples, and it has a better repair effect. Moreover, the repair effect of the injection method is significantly higher than those of the perfusion and immersion methods, and the ultrasonic wave transit time decreases by 1.22% on average. Based on the combination of quartz sand and EICP repair methods, the calcium carbonate precipitated among the sand granules contributes to a binding effect that strengthens the cohesive force among the sand granules.
PubMed: 38930347
DOI: 10.3390/ma17122978 -
Materials (Basel, Switzerland) Jun 2024This paper shows the three-point bending strength analysis of a composite material consisting of polyamide doped with chopped carbon fiber and reinforced with continuous...
This paper shows the three-point bending strength analysis of a composite material consisting of polyamide doped with chopped carbon fiber and reinforced with continuous carbon fiber produced by means of the material extrusion (MEX) additive manufacturing technique. For a comparison, two types of specimens were produced: unreinforced and continuous fiber-reinforced (CFR) with the use of carbon fiber. The specimens were fabricated in two orientations that assure the highest strength properties. Strength analysis was supplemented by additional digital image correlation (DIC) analysis that allowed for the identification of regions with maximum strain within the specimens. The utilization of an optical microscope enabled a fractographic examination of the fracture surfaces of the specimens. The results of this study demonstrated a beneficial effect of continuous carbon fiber reinforcement on both the stiffness and strength of the material, with an increase in flexural strength from 77.34 MPa for the unreinforced composite to 147.03 MPa for the composite reinforced with continuous carbon fiber.
PubMed: 38930305
DOI: 10.3390/ma17122937 -
Materials (Basel, Switzerland) Jun 2024The application of advanced high-strength steel grades (AHSS) in different kinds of industry is connected to more than their attractive mechanical properties. The...
The application of advanced high-strength steel grades (AHSS) in different kinds of industry is connected to more than their attractive mechanical properties. The present paper focuses on improving the welding Docol 1300M steel to reach an acceptable microstructure and mechanical parameters. It was decided to manufacture joints with different welding parameters using different filler materials. The electrode wires were varied to increase the carbon content in the weld, and nitrogen was added to the argon shielding mixture to obtain non-metallic inclusions that strengthen the fusion zone. Specimens of joints welded with the gas metal arc welding (GMAW) process for non-destructive and destructive tests were examined. Tensile and bending tests as well as microscopic inspections using a light (LM) and scanning electron microscope (SEM) were also conducted. The results from the fatigue test confirmed the validity of the proposed welding process for the Docol 1300M joint. The collected data enabled the following conclusion: The article's novelty is represented by the use of shielding gas mixtures containing argon and nitrogen in the GMAW welding process of AHSS steel to create titanium non-metallic inclusions, which will translate into better performance properties of the entire joint.
PubMed: 38930303
DOI: 10.3390/ma17122934 -
Materials (Basel, Switzerland) Jun 2024The lower valence compensation of YMnCuO ( = 0.00, 0.05, and 0.10) is prepared by the solid-state reaction, and the effects of divalent cation Cu-doping on the...
The lower valence compensation of YMnCuO ( = 0.00, 0.05, and 0.10) is prepared by the solid-state reaction, and the effects of divalent cation Cu-doping on the construction and magnetic and dielectric attributes of multiferroic YMnO are systemically researched. Powder X-ray diffraction shows YMnCuO has a single-phase hexagonal construction with a space group as the parent YMnO, and lattice parameters decrease systematically as Cu concentration increases. Using the scanning electric microscope, structure morphologies analysis shows that the mean grain size varies between 1.90 and 2.20 μm as Cu content increases. YMnCuO magnetization increases as Cu doping concentration increases, and the antiferromagnetic transition temperature declines from 71 K for = 0.00 to 58 K for = 0.10. The valence distributions of Mn ions conduce to the modified magnetic attributes. Due to Cu substitution, the dielectric loss and dielectric constant decline as frequency increases from 400 to 700 K, showing representative relaxation behaviors. Indeed, that is a thermally activated process. In addition, the peak of the dielectric loss complies with the Arrhenius law. The relaxation correlates to the dipole effect regarding carrier hopping between Mn and Mn, and also correlates to oxygen vacancies generated by Mn.
PubMed: 38930298
DOI: 10.3390/ma17122929 -
Materials (Basel, Switzerland) Jun 2024The paper presents the study concerning the preparation and physio-chemical and biological properties of wool-copper (WO-Cu) materials obtained by the sputter deposition...
The paper presents the study concerning the preparation and physio-chemical and biological properties of wool-copper (WO-Cu) materials obtained by the sputter deposition of copper onto the wool fibers. The WO-Cu material was subjected to physio-chemical and biological investigations. The physio-chemical investigations included the elemental analysis of materials (C, N, O, S, and Cu), their microscopic analysis, and surface properties analysis (specific surface area and total pore volume). The biological investigations consisted of the antimicrobial activity tests of the WO-Cu materials against colonies of Gram-positive () bacteria, Gram-negative () bacteria, and fungal mold species (). Biochemical-hematological tests included the evaluation of the activated partial thromboplastin time and pro-thrombin time. The tested wool-copper demonstrated the ability to interact with the DNA in a time-dependent manner. These interactions led to the DNA's breaking and degradation. The antimicrobial and antifungal activities of the WO-Cu materials suggest a potential application as an antibacterial/antifungal material. Wool-copper materials may be also used as customized materials where the blood coagulation process could be well controlled through the appropriate copper content.
PubMed: 38930247
DOI: 10.3390/ma17122878