Search Results (71)

Stabilization of the resonance frequency in thin-film acoustic devices to variations in environmental conditions is commonly reduced to the passive or active compensation of a single factor (usually temperature) and the isolation or addition of a separate correction circuit for every other factor (e.g., pressure and mass loading). In this work, the possibility of dual-factor compensation is proposed, where the response of a multi-layered thin structure to both temperature and ambient pressure variation vanishes due to the choice of intrinsic parameters (materials and thickness ratios). The response functions are derived for the $S_0$ Lamb mode at long wavelengths in an explicit analytical form in terms of bulk material characteristics. It is demonstrated that the dual-factor intrinsic stabilization requires at least a three-layered structure and can be achieved for materials commonly used in temperature-compensated devices (aluminum nitride, fused silica, and aluminum). Identification of the key material characteristics governing the existence of a stability solution can serve for a targeted search of such composites and implementation of new thin-film dual devices. Full article

The composition of plastic and multilayer packaging waste was assessed in the mixed municipal solid waste (MSW) streams of the Kaunas (Lithuania), Daugavpils (Latvia) and Tallinn (Estonia) municipalities. For the analysis of samples in the mixed MSW streams, the authors used manual sorting and a visual recognition method. Composition analysis of plastic and multilayer packaging waste from separately collected waste of multi-family and single-family households was performed in the Kaunas and Tallinn municipalities. For the analysis of samples in the separately collected waste streams, the research group combined manual sorting and near-infrared (NIR) spectroscopy methods. The findings reveal that the percentage distribution of plastic and multilayer packaging waste within the municipal solid waste (MSW) stream is relatively consistent across the municipalities of Kaunas, Daugavpils and Tallinn, comprising 40.16%, 36.83% and 35.09%, respectively. However, a notable variation emerges when examining separately collected plastic and multilayer packaging waste streams. In this category, the proportion of plastic and multilayer packaging within the total separately collected packaging waste stream ranges from 62.05% to 74.7% for multi-family residential buildings and from 44.66% to 56.89% for single-family residential buildings. The authors provided further insights for the enhanced recycling potential of different plastic materials through improved sorting. Full article

The porous structure, in which many pores are intentionally placed inside the material, has excellent impact energy absorption properties. Recent studies have attempted to fabricate multi-layered porous structures with different mechanical properties within a single porous structure sample, and the mechanical properties of these structures are being elucidated. However, these studies mainly attempted to vary the densities, pore structures, and alloy compositions within a single material, such as aluminum, for the entire sample. Since multi-materials are now being promoted to utilize the most suitable material type in the right place, porous structures made of different materials, such as a combination of aluminum and resin, are expected to be required in the future. In this study, we attempted to fabricate two-layered porous structure samples of different materials by printing a resin porous structure using a 3D printer on an aluminum foam fabricated by a precursor foaming process. Static compression tests were performed on the resulting two-layered porous structure samples to investigate their mechanical properties. The resin porous structure printed by the 3D printer and the aluminum foam were both designed to expose the porous structure on the surface of the specimen so that the deformation behavior can be easily observed. The density of the resin porous structure was varied by systematically varying the filling rate of the resin porous structure to be printed, and the effect on the compression properties was investigated. The fabricated two-layered porous structure was effectively bonded between the two layers by the anchor effect, which is a mechanical bonding caused by the resin penetrating into the pores. The layers exhibited robust bonding with no evidence of separation. It was possible to fabricate a two-layered porous structure that exhibited both properties of aluminum foam and those of resin porous structure. It was found that the plateau stress in the resin porous structure layer can be controlled between about 0.5 MPa and 40 MPa, and the deformation behavior and energy absorption properties of the two-layered porous structure can be controlled by varying the resin filling rate of the resin porous structure layer. That is, it was indicated that multi-layered porous structures with various densities and consisting of various types of materials allow for the optimal design of porous structures used in structural materials. Full article

A multilayer structure is a type of construction consisting of outer layers and a core, which is mainly characterized by high strength and specific stiffness, as well as the ability to dampen vibration and sound. This structure combines the high strength of traditional materials (mainly metals) and composites. Currently, sandwich structures in any configurations (types of core) are one of the main directions of technology development and research. This paper evaluates the surface quality of II- and III-layer sandwich structures that are a combination of aluminum alloy and CFRP (Carbon Fiber-Reinforced Polymer) after the machining. The effect of depth of cut (a_e) on the surface roughness of the II- and III-layer sandwich structures after the milling process was investigated. The surface homogeneity was also investigated. It was expressed by the I_Ra and I_Rz surface homogeneity indices formed from the Ra and Rz surface roughness parameters measured separately for each layer of the materials forming the sandwich structure. It was noted that the lowest surface roughness (Ra = 0.03 µm and Rz = 0.20 µm) was obtained after the milling of the II-layer sandwich structure using a_e = 0.5 mm, while the highest was obtained for the III-layer structure and a_e = 1.0 mm (Ra = 1.73 µm) and a_e = 0.5 mm (Rz = 10.98 µm). The most homogeneous surfaces were observed after machining of the II-layer structure and using the depth of cut a_e = 2.0 mm (I_Ra = 0.28 and I_Rz = 0.06), while the least homogeneous surfaces were obtained after milling of the III-layer structure and the depths of cut a_e = 0.5 mm (I_Ra = 0.64) and a_e = 2.0 mm (I_Rz = 0.78). The obtained results may be relevant to surface engineering and combining hybrid sandwich structures with other materials. Full article

Objectives: This study aimed to develop an optimized and wide concentration range HPLC-UV method for fluconazole (FLU) determination and its adaptation for pharmacokinetics (PK) studies in the pediatric population. Methods: The following parameters of chromatographic separation were optimized: retention time, tailing factor, peak height, and the sample preconditioning parameter, such as recovery. The optimization process involved the use of a central composite design (CCD) and Box–Behnken design (BBD) in the design of experiments (DoE) approach and a multilayer perceptron (MLP) for artificial neural network (ANN) application. Statistical and PK analyses were performed using Statistica and PKanalix. Results: The acetonitrile (ACN) concentration revealed the most significant factor influencing the retention time, tailing factor, and peak height of FLU and the internal standard. For recovery, the extracting agent’s volume was the most significant factor. In most cases, the analysis conducted with the DoE and ANN indicated the same factors in a similar order regarding their impact on the analyzed variables. The optimization process allowed for achieving a wide range of determined concentrations (0.5–100 mg/L) and ~100% recovery. The developed method enabled PK analysis of 12 samples from three pediatric patients, proving its clinical usability. The estimated median clearance (CL) and volume of distribution (Vd) were 1.01 L/h and 18.64 L, respectively. Conclusions: DoE and ANNs are promising and useful tools in the optimization of sample preconditioning as well as the HPLC separation procedure. The investigated fluconazole determination method meets the European Medicines Agency (EMA) validation objectives and might be used in pediatric and adult PK studies. Full article

The combined pollution of organics and heavy metals represents a significant environ-mental problem that has attracted widespread attention. This explores the treatment of methylene blue (MB) and Cu(II), which are common pollutants in dye wastewater, and the recycling of Cu. A magnetized vaterite (V-M) was synthesized using Bacillus velezensis, and its structure and magnetic performance were investigated. The effects and mechanisms of removing MB-Cu(II) composite pollution using V-M and H₂O₂ in combination were estimated. The results indicated that V-M is a combination of organic and inorganic substances, with 21.5 wt% organic matter and multiple organic functional groups, including O-H, -SH, and others. The combination of V-M and H₂O₂ can achieve a maximum removal percentage of 90% for MB-Cu(II) pollution. The analysis showed that MB was oxidized by the ·OH generated from the H₂O₂-based Fenton-like reaction, and was catalyzed by the Fe₃O₄ in V-M. The immobilization of Cu(II) by V-M was mostly realized through the binding of the organic substances on the surface of the V-M, multilayer adsorption, and a replacement reaction with Ca(II). Magnetic separation and the addition of diluted HCl were used for the recycling of the Cu(II) enriched by V-M, with a recycling percentage reaching 85%. This study introduced a novel approach to the remediation of MB-Cu(II) composite pollution, and the recycling of Cu(II). Full article

For monitoring capillary moisture conduction, the most important parameter is the moisture conductivity coefficient, which is a material characteristic; however, its use in practical calculations is not very common. For further development in the field of liquid moisture propagation, an automated measuring apparatus has been developed and granted a European patent. Its essence lies in detecting the liquid water content based on a well-known physical phenomenon: electromagnetic radiation in the microwave range. The determination of the spatiotemporal moisture field is the first and fundamental step for describing transportation phenomena. The moisture field thus created allows for the viewing of the moisture conductivity coefficient, which is one of the most important parameters in describing transportation phenomena as a function of moisture. The presence of water in building materials can significantly affect their physical properties, such as mechanical or thermal–technical characteristics. This may lead to unacceptable consequences, which might only manifest after a certain period of time. In the case of multi-layered structures, moisture can transfer from one material to another. Therefore, it is essential to address this process. The advantage of the software solution described by the methodology is the use of an open communication protocol in the form of a synchronized array, which is not common in typical applications of this type. The principle of separating hardware modules is also unusual for devices of this type, as it requires the independent communication of each module with the control software. Mutual communication is handled exclusively at the software level, making it possible to modify, optimize, or parameterize the procedures as needed. Upon closer examination of the wetting curves of various materials, anomalies were revealed in some of their structures. This can be advantageously utilized in the research of newly developed composite materials. The assembled system of measuring instruments, their software integration, and control provide a foundation for the practical application of the described procedures and methods for determining the moisture field of building materials. The parameterization of individual processes, as well as the open access to data, allows for the optimization of the methodology, as materials of entirely different characteristics may require an individual approach, which will certainly contribute to the advancement of science and research in this area. Currently, this work is being followed by further extensive studies, not yet published by the authors, focusing on the application of the described moisture field to evaluate the moisture conductivity coefficient as a function dependent on the material’s mass moisture content. Their application requires specific mathematical and programming approaches due to the significant volume of data involved. Full article

The ability to trace the origin of eggs from backyard-raised hens is important due to their higher market value compared to barn-raised eggs. This study aimed to differentiate eggs from these two rearing systems using isotopic, elemental, and fatty acid profiles of egg yolks. A total of 90 egg yolk samples were analyzed, analytical results being followed by statistical tests (Student’s t-test) showing significant differences in δ¹⁸O, several elements (Mg, K, Sc, Mn, Fe, Ni, Cu, Zn, As, Cd, Ba, Pb), and fatty acids compositions (C23:0, C17:0, C18:0, C16:1n7, C18:1n9, C18:2n6, C20:1n7, C20:4n6, C20:5n3, C22:6n3), as well as in the ratios of SFA, PUFA, and UFA. The results indicated a nutritional advantage in backyard eggs due to their lower n-6 polyunsaturated fatty acid content and a more favorable n-6 to n-3 ratio, linked to differences in the hens’ diet and rearing systems. To classify the production system (backyard vs. barn), three pattern recognition methods were applied: linear discriminant analysis (LDA), k–nearest neighbor (k–NN), and multilayer perceptron artificial neural networks (MLP–ANN). LDA provided perfect initial separation, achieving 98.9% accuracy in cross-validation. k-NN yielded classification rates of 98.4% for the training set and 85.7% for the test set, while MLP–ANN achieved 100% accuracy in training and 92.3% in testing, with minor misclassification. These results demonstrate the effectiveness of fusion among isotopic, elemental, and fatty acid profiles in distinguishing backyard eggs from barn eggs and highlight the nutritional benefits of the backyard-rearing system. Full article

Heterogeneous microstructures in Cu-Mo-W alloy thin films formed by magnetron co-sputtering immiscible elements with concentrated compositions are characterized using scanning transmission electron microscopy (STEM) and nanoindentation. In this work, we modified the phase separated structure of a Cu-Mo immiscible system by adding W, which impedes surface diffusion during film growth. The heterogeneous microstructures in the Cu-Mo-W ternary system exhibited bicontinuous matrices and agglomerates composed of Mo(W)-rich phase. This is unique, as these are the slower-diffusing species, contrasting past reports of binary Cu-Mo thin films that exhibited Cu-rich agglomerates. The bicontinuous matrices comprised of Cu-rich and Mo(W)-rich phases exhibited bilayer thicknesses of less than 5 nm. The hardness of these thin films measured using nanoindentation is reported and compared to similar multilayers and nanocomposites in binary systems. Full article

Carboxymethyl cellulose (CMC) and polylactic acid (PLA) are recognized for their environmental friendliness. By merging them into a composite film, packaging solutions can be designed with good performance. Nonetheless, the inherent interface disparity between CMC and PLA poses a challenge, and there may be layer separation issues. This study introduces a straightforward approach to mitigate this challenge by incorporating tannin acid and ferric chloride in the fabrication of the CMC−PLA. The interlayer compatibility was improved by the in situ formation of a cohesive interface. The resulting CMC/TA−PLA/Fe multilayer film, devoid of any layer separation, exhibits exceptional mechanical strength, with a tensile strength exceeding 70 MPa, a high contact angle of 105°, and superior thermal stability. Furthermore, the CMC/TA−PLA/Fe film demonstrates remarkable efficacy in blocking ultraviolet light, effectively minimizing the discoloration of various wood surfaces exposed to UV aging. Full article

Nowadays, yttria (Y³⁺)-stabilized ZrO₂ (Y-TZP) is the most commonly used material in dental prosthetics. Y-TZP dental ceramics are mainly stabilized via the addition of 3 mol% yttrium oxide (Y₂O₃). These ceramics exhibit excellent mechanical properties, including high flexural strength, fracture toughness, elastic modulus, etc. Some manufacturers have recently introduced a new class of dental materials with multilayer composition with the aim of combining the advantages of adding more or less Y₂O₃ to the ceramic composition in one Y-TZP material. The flexural strength values of multilayer Y-TZP may vary depending on the dimensions of the specimen, layer distributions, and especially the layer exposed on the maximum tension side, i.e., loading configuration. Although previous studies have examined the flexural strength of separate Y-TZP layers, capturing the flexural strength of multilayer Y-TZP is still challenging. However, one should keep in mind that multilayer flexural strength is important for clinical indications. The objective of this study is to compare the flexural strength of three distinct multilayer translucent Y-TZP materials made up of layers with different Y³⁺ contents. Rectangular samples (2 mm × 2 mm × 16 mm) were prepared from CAD/CAM discs using the milling machine Programill PM7 (Ivoclar Vivadent AG). Milled bars were tested for flexural strength in a three-point bending test (ISO 6872:2015) using a universal testing machine (Inspekt Duo 5kN; Hegewald & Peschke, Nossen, Germany) at a crosshead speed of 0.5 mm/min. Representative samples of each type of material were selected for quantitative and qualitative analysis of the microstructure. Representative samples of each type of material were selected for structural, mechanical, and microstructural analyses. Full article

The need to reduce energy consumption in buildings, the emergence of light-emitting diode (LED) lamps in lighting around 2010, their long lifetime, and the 2025 target to use only LED lamps are changing the existing composition of Category 3 waste electrical–electronic equipment (WEEE) and creating expectations for simple, high-concentration recycling streams. In this study, multi-layer ceramic capacitors (MLCCs) detached from the lighting sector’s WEEE were characterised for the presence of rare earth elements (REEs) and precious metals (PMs). Their digestion was carried out with HNO₃ and aqua regia on a heating plate and characterised using inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). The contents of REEs and PMs found in the MLCCs were 0.84 wt% and 0.60 wt%, respectively, and create an economic stored value that is essentially defined by PMs of 98.67% and by palladium (Pd) of 78.37%. The analysis showed that the content of the main elements was: neodymium (Nd) 0.366 wt%, yttrium (Y) 0.220 wt%, dysprosium (Dy) 0.131 wt%, silver (Ag) 0.467 wt%, and Pd 0.105 wt%. These results indicate the need for selective removal and separate recycling processes of MLCCs from WEEE drivers. Full article

This study deals with the combination of two corrosion protection strategies for aluminium: barrier protection (provided by a 3.8 μm thick hybrid sol–gel coating) and aluminium pore sealing via the use of a 100 nm thick layer of aluminium oxide. A Si–O–Zr hybrid sol–gel coating (TMZ) was synthesised by combining two separately prepared sols (i) tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane and (ii) zirconium(IV) n-propoxide chelated with methacrylic acid. The synthesis of the Si–O–Zr hybrid sol–gel was evaluated at various stages using real-time infrared spectroscopy. A 100 nm thick Al₂O₃ film was prepared via thermal atomic layer deposition at 160 °C using trimethyl aluminium and water as precursors. The coating and film properties were assessed via focused ion beam/scanning electron microscopy coupled with energy-dispersive X-ray spectrometry. Sealing with the Al₂O₃ film did not affect the microstructure and composition of the underlying sol–gel coating. The coating’s corrosion performance in 0.1 M NaCl solution was evaluated using electrochemical impedance spectroscopy. Compared to individual coatings, the multilayer TMZ/Al₂O₃ coating ensured prolonged (more than three weeks) durable corrosion protection for the aluminium. The impedance magnitude increased by two orders compared to the uncoated substrate (|Z|_{10 mHz} from 16 kΩ cm² to almost 830 MΩ cm²). Thus, the pore sealing of the sol–gel coating using an ALD alumina film produced a protective multilayer coating system, with |Z|_{10 mHz} remaining above 5 MΩ cm² after four weeks in NaCl solution. Full article

Hundreds of thousands of kilometers of communication and power (umbilical) cables and flowlines lie undersea worldwide. Most of these offshore cables and flowlines have reached or will soon be nearing the end of their service life, prompting the need for a viable recycling approach to recover some valuable material, e.g., copper. However, separation into constituent materials has proven very challenging due to the highly robust design of the composite cables (and flowlines) to withstand service conditions and the tough external plastic sheaths that protect against seawater corrosion. This study aims at promoting sustainable practices in the offshore energy sector. Here, we summarize the findings of the cryogenic comminution of subsea cables and flowlines for an effective separation and recovery of component materials. Heat transfer analyses of complex multilayer flowlines and umbilicals were conducted to evaluate the time required for these structures to reach their respective critical brittle-transition temperatures. Subsequently, the time was used as a guide to crush the flowline and umbilical cables under cryogenic conditions. The results show that the flowlines and umbilical cables will reach the brittle-transition temperature after approximately 1000s (i.e., 17 min) of submergence in liquid nitrogen (LN). Comminution of the materials at temperatures near the brittle-transition temperature was proven relatively efficient compared to room-temperature processing. The present evaluation of heat transfer and lab-scale crushing will afford accurate process modelling and design of a pilot cryogenic comminution of decommissioned subsea cables and flowlines, enabling the sustainable recovery of valuable materials that can provide a new stream of waste-to-wealth economy. Full article

MXene exhibits impressive characteristics, including flexibility, mechanical robustness, the capacity to cleanse liquids like water through MXene membranes, water-attracting nature, and effectiveness against bacteria. Additionally, bacterial cellulose (BC) exhibits remarkable qualities, including mechanical strength, water absorption, porosity, and biodegradability. The central hypothesis posits that the incorporation of both MXene and bacterial cellulose into the material will result in a remarkable synthesis of the attributes inherent to MXene and BC. In layered MXene/BC coatings, the presence of BC serves to separate the MXene layers and enhance the material’s integrity through hydrogen bond interactions. This interaction contributes to achieving a high mechanical strength of this film. Introducing cellulose into one layer of multilayer MXene can increase the interlayer space and more efficient use of MXene. Composite materials utilizing MXene and BC have gained significant traction in sensor electronics due to the heightened sensitivity exhibited by these sensors compared to usual ones. Hydrogel wound healing bandages are also fabricated using composite materials based on MXene/BC. It is worth mentioning that MXene/BC composites are used to store energy in supercapacitors. And finally, MXene/BC-based composites have demonstrated high electromagnetic interference (EMI) shielding efficiency. Full article