Materials, Volume 16, Issue 24 (December-2 2023) – 203 articles

Surface coating has been widely used to ameliorate the surface properties of Ti alloys. In this study, high-power pulsed magnetically controlled sputtering technology was used to successfully prepare a nano-CrN/TiN multi-layered coating on the surface of a TC4 Ti alloy. The surface of the obtained coating was uniform, dense, and free of obvious defects. With the decrease in modulation period, the optimal growth of the nano-CrN/TiN multi-layered coating was changed from a (220) crystal surface to (111) and a (200) crystal surface. Compared to the single-layered CrN or TiN coating, the nano-multi-layered coating had higher hardness and lower wear rate. Furthermore, the hardness and the wear resistance increased with the decrease in the modulation period. This presented an optimal modulation period of 6 nm. Meanwhile, the resistance of the obtained coating to high-temperature oxidation at 800 °C was also significantly improved. Full article

Slags and ashes generated in thermal waste treatment facilities require proper management. In line with the principles of the circular economy, new, more economical, and ecological possibilities for utilizing these substances are sought. These waste materials exhibit characteristics similar to rocks in many aspects. This study focuses on analyzing the similarities and differences between nine selected rocks and three samples of slags and ashes obtained from municipal waste incineration. The main research device used was a polarizing microscope, using reflected, transmitted, and fluorescent light. Additionally, low-pressure gas adsorption equipment, as well as helium and quasi-liquid pycnometers, were used for complementary analysis. The parameters analyzed mainly covered broadly defined petrographic properties of rocks and slags, with a particular emphasis on porosity, porous structure, and the spatial distribution of pores and fractures. The conducted analyses confirmed a significant similarity between slags and ashes and clastic sedimentary rocks such as sandstones and mudstones. The research results underscore the importance of petrographic microscopic studies for analyzing materials other than rocks. They also allow for exploring applications for slags and ashes in areas traditionally reserved for natural rock resources. The findings also indicate the necessity of using methods other than microscopic ones to describe the pore space of rocks. The lower measurement range of the optical microscope is limited to approximately 1 μm, covering only macropores. Other methods extend this characteristic to micro- and mesopores. Therefore, a combination of different methods is often employed to obtain a more comprehensive characterization of rock porosity. Full article

In this paper, the feasibility of multi-walled carbon nanotube (MWCNT)-modified clay as a landfill liner material is investigated. Experiments were conducted on the modified clay with 0.5%, 1%, and 2% MWCNTs. The effects of the MWCNTs on the compaction characteristics, permeability coefficient, stress–strain curve, peak deviation stress, shear strength parameters (internal friction angle and cohesion), microstructures, and adsorption performance of the clay were analyzed. The results showed that the optimum moisture content (OMC) increased from 16.15% to 18.89%, and the maximum dry density (MDD) decreased from 1.79 g/cm³ to 1.72 g/cm³ with the increase in MWCNTs. The permeability coefficients firstly fell and then gradually rose as the MWCNTs increased; the minimum permeability coefficient was 8.62 × 10⁻⁹ cm/s. The MWCNTs can also effectively increase the peak deviation stress of the clay, and at the maximum level, the peak deviation stress was increased by 286%. SEM images were processed using the Pore and Crack Analysis System (PCAS), and the results showed that the appropriate amount of MWCNTs could fill the pores and strengthen the clay structure. The effect of the MWCNT-modified clay on the adsorption performance of common heavy metal ions Cd²⁺, Mn²⁺ and Cu²⁺ in landfill leachate was analyzed by batch adsorption tests. The maximum adsorption capacities (Q_max) of Cu²⁺, Cd²⁺ and Mn²⁺ in the 2% MWCNT-modified clay were, respectively, 41.67 mg/g, 18.69 mg/g, and 4.97 mg/g. Compared with the clay samples without MWCNTs, the adsorption properties of Cu²⁺, Cd²⁺, and Mn²⁺ were increased by 228%, 124%, and 202%, respectively. Overall, the results suggest that MWCNT-modified clays have the potential to be suitable barrier materials for the construction of landfills. Full article

The modification mechanism of low-molecular-weight organic acids on a single-chain silicate mineral (wollastonite) was investigated through a leaching method. Solid and liquid samples were analyzed using atomic absorption spectrophotometer (AAS), X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR). After 720 h of reaction, the results revealed that the dissolution concentration of Si (2200 μmol/L) in citric acid solution is more than that (1950 μmol/L) in oxalic acid. In the composite acids (citric acid and oxalic acid), the dissolution concentration of Si release from wollastonite reached the maximum value of 3304 μmol/L. The dissolution data of Si in wollastonite were fittingly described by the parabolic equation (Ct = a + bt^1/2), with the highest correlation coefficients (R² > 0.993), in the presence of the low-molecular-weight organic acids. The dissolution data suggested that the dissolution reaction process of Si was consistent with the diffusion-controlled model. Citric acid exhibited a higher affinity for attacking the (200) surface, while oxalic acid was prone to dissolve the (002) crystal face. The synergistic effects of oxalic acid and citric acid led to the weakening of the XRD diffraction peak intensity of wollastonite. When exposed to composite acids, the surface of wollastonite was covered with insoluble reactants that restricted the substance diffusion and hindered the reaction. This study offers valuable theoretical insights into the modification or activation of wollastonite by composite low-molecular-weight organic acids. Full article

The Qinghai–Tibet Plateau is the main permafrost area in China. Concrete structures constructed on permafrost are affected by the early negative-temperature environment. In particular, the negative-temperature environment seriously affects the strength growth process and the frost resistance of concrete (FRC). Therefore, this study considered the influence of the gas content, water–binder ratio (w/b), age, and other factors on the strength variation law and FRC under −3 °C curing conditions. Nuclear magnetic resonance (NMR) was used to analyze the pore structure of concrete before and after freeze–thaw cycles (FTCs). The results showed that the compressive strength of the concrete (CSC) under −3 °C curing was only 57.8–86.4% of that cured under standard conditions. The CSC under −3 °C curing showed an obvious age-lag phenomenon. The FRC under −3 °C curing was much lower than that under standard curing. The porosity of the concrete under −3 °C curing was greater, with a higher percentage of harmful and multi-harmful pores than that under standard curing. The concrete properties deteriorated primarily because curing at −3 °C hindered the hydration reaction compared with standard methods. This hindrance resulted in diminished hydration development, weakening the concrete’s structural integrity. Under both curing conditions, when the gas content was between 3.2% and 3.8%, the frost resistance was the best. This is because a gas content within this range effectively enhances the internal pore structure, therefore relieving the swelling pressure caused by FTCs. Based on the freeze–thaw damage (FTD) model proposed by previous authors, a new model for the CSC under −3 °C curing reaching that of the concrete under standard curing for 28 d was established in this study. This advanced model was capable of accurately assessing the FTD of concrete structures in permafrost regions. Finally, the life expectancy of concrete in Northwest China was predicted. The life of the concrete reached 46.9 years under standard curing, while the longest life of the concrete under −3 °C curing was only 12.9 years. Therefore, attention should be paid to constructing and curing concrete structures in cold environments. Full article

This manuscript presents the synthesis of hyperbranched amphiphilic poly (lauryl methacrylate-co-tert-butyl methacrylate-co-methacrylic acid), H-P(LMA-co-tBMA-co-MAA) copolymers via reversible addition fragmentation chain transfer (RAFT) copolymerization of tBMA and LMA, and their post-polymerization modification to anionic amphiphilic polyelectrolytes. The focus is on investigating whether the combination of the hydrophobic characters of LMA and tBMA segments, as well as the polyelectrolyte and hydrophilic properties of MAA segments, both distributed within a unique hyperbranched polymer chain topology, would result in intriguing, branched copolymers with the potential to be applied in nanomedicine. Therefore, we studied the self-assembly behavior of these copolymers in aqueous media, as well as their ability to form complexes with cationic proteins, namely lysozyme (LYZ) and polymyxin (PMX). Various physicochemical characterization techniques, including size exclusion chromatography (SEC) and proton nuclear magnetic resonance (¹H-NMR), verified the molecular characteristics of these well-defined copolymers, whereas light scattering and fluorescence spectroscopy techniques revealed promising nanoparticle (NP) self- and co-assembly properties of the copolymers in aqueous media. Full article

The present work is focused on nickel catalysts supported on La₂O₃-CeO₂ binary oxides without and with the addition of Cu to the active component for the dry reforming of methane (DRM). The catalysts are characterized using XRD, XRF, TPD-CO₂, TPR-H₂, and low-temperature N₂ adsorption–desorption methods. This work shows the effect of different La:Ce ratios (1:1 and 9:1) and the Cu addition on the structural, acid base, and catalytic properties of Ni-containing systems. The binary LaCeO_x oxide at a ratio of La:Ce = 1:1 is characterized by the formation of a solid solution with a fluorite structure, which is preserved upon the introduction of mono- or bimetallic particles. At La:Ce = 9:1, La₂O₃ segregation from the solid solution structure is observed, and the La excess determines the nature of the precursor of the active component, i.e., lanthanum nickelate. The catalysts based on LaCeO_x (1:1) are prone to carbonization during 6 h spent on-stream with the formation of carbon nanotubes. The Cu addition facilitates the reduction of the Cu-Ni catalyst carbonization and increases the number of structural defects in the carbon deposition products. The lanthanum-enriched LaCeO_x (9:1) support prevents the accumulation of carbon deposition products on the surface of CuNi/La₂O₃-CeO₂ 9:1, providing high DRM activity and an H₂/CO ratio of 0.9. Full article

Radiation-shielding clothing for medical workers must be light and thin, thus ensuring flexibility. However, controlling the thickness and weight is limited by shielding performance requirements. This study aims to improve shielding performance by considering a shielding structure that mimics the internal structure of an abalone shell. Two shields were produced: a sheet made with a carrier process using a liquid polymer and tungsten mixture, and a fillet made by compounding the same material and laminated using a heat-treatment press after the injection process. The tungsten content and thickness were the same at 85 wt% and 0.3 mm, respectively. In the high-energy region, the shielding film based on the laminated structure of abalone shells showed a shielding rate that was higher by more than 7%. Compared to that of a 0.3 mm lead plate, the shielding ratio of the shielding film was approximately 16% lower at 120 kVp, thereby confirming the radiation-shielding effect of the layered-structure shielding film. Therefore, it is concluded that the laminated structure of the shielding film, which is identical to the internal laminated structure of the abalone shell, expands the impact area of incident radiation and attenuates the energy intensity, thereby improving the medical-radiation-shielding performance. Full article

Mastering the variations in the stability of a polarization vortex is fundamental for the development of ferroelectric devices based on polarization vortex domain structures. Some phase field simulations were conducted on PbTiO₃ nanofilms with an initial polarization vortex under uniaxial tension or compression to investigate the conditions of vortex instability and the effects of aspect ratio of nanofilms and temperature on them. The instability of a polarization vortex is strongly dependent on aspect ratio and temperature. The critical compressive stress increases with decreasing aspect ratio under the action of compressive stress. However, the critical tensile stress first decreases and then increases with decreasing aspect ratio, then continues to decrease. There are two inflection points in the curve. In addition, an elevated temperature makes both the critical tensile and compressive stresses decline, and will also cause the aspect ratio corresponding to the inflection point to decrease. These are very important for the design of promising nano-ferroelectric devices based on polarization vortices to improve their performance while maintaining storage density. Full article

High-quality steels are defined primarily by a small quantity of non-metallic inclusions and a high degree of chemical homogenisation. The ladle furnace (LF) is the most important metallurgical unit in which the quantity of non-metallic inclusions can be significantly reduced while ensuring metal chemical homogenisation. It is achieved largely due to appropriate controlling and the use of increasingly developed inert gas purging techniques. Various types of porous plugs (channel or radial type) are used in the metallurgical ladles. In aggregate units of intermediate-ladle type, various types of channel plugs and/or gas curtains are successfully used. In the research presented herein, a new and innovative module for inert gas injection into liquid steel for deep refining was tested. The presented research relates to the innovative module using to replace the standard porous plug in the steelmaking ladle on the outside-furnace (LF) processing station. Hybrid modelling methods (numerical and physical modelling) were used to carry out research. Module using causes significantly faster alloy additive dispersion in ladle volume compared with the standard solution (the standard porous plug). Furthermore, the obtained flowing structure positively affects liquid steel refining and mixing processes after alloy additive addition. A new technological solution, i.e., gas-injection module—differs from the traditional porous plugs currently used in the steel mills in terms of geometric parameters, external and internal structure, and what is most importantly, terms of the active surface area—shall be understood in as the surface area wherein slots occur. Full article

Leaching in cement-based materials and dissolution in rocks are important problems in civil engineering. In the past century, concrete damage caused by leaching have occurred worldwide. And, rock dissolution is usually the main cause of karst rock erosions. This paper provides a review of the causes, influencing factors, and effects on engineering properties of dissolution of rocks and leaching of cement-based materials. The applied experimental methods for leaching and dissolution have been sorted out and discussed. In situ field experiments can be used to study dissolution under natural conditions, while the laboratory experiments can effectively shorten the experiment time length (by changing pH, temperature, pressure or other factors that affect the leaching or dissolution) to quickly investigate the mechanism of dissolution and leaching. Micro tests including XRD, SEM, EDS, and other testing methods can obtain the changes in material properties and microstructures under leaching and dissolution. In addition, with the advances in technologies and updated instruments, more and more new testing methods are being used. The factors affecting the leaching and dissolution include environmental factors, materials, and solvent parameters. The mechanisms and deterioration processes of leaching and dissolution varies according to the types of material and the compositions. Full article

Water pollution is a big problem for the environment, and thus depollution, especially by adsorption processes, has garnered a lot of interest in research over the last decades. Since sorbents would be used in large quantities, ideally, they should be cheaply prepared in scalable reactions from waste materials or renewable sources and be reusable. Herein, we describe a novel preparation of a range of magnetic sorbents only from waste materials (sawdust and iron mud) and their performance in the adsorption of several dyes (methylene blue, crystal violet, fast green FCF, and congo red). The preparation is performed in a hydrothermal process and is thus easily scalable and requires little sophisticated equipment. The magnetic nanostructured materials were analyzed using FTIR, VSM, SEM/EDX, XRD, and XPS. For crystal violet as a pollutant, more in-depth adsorption studies were performed. It was found that the best-performing magnetic sorbent had a maximum sorption capacity of 97.9 mg/g for crystal violet (methylene blue: 149.8 mg/g, fast green FCF: 52.2 mg/g, congo red: 10.5 mg/g), could be reused several times without drastic changes in sorption behavior, and was easily separable from the solution by simply applying a magnet. It is thus envisioned to be used for depollution in industrial/environmental applications, especially for cationic dyes. Full article

Convection has a nonnegligible effect on the growth of the magnesium dendrite with six-primary-branch pattern. Most work, however, investigates the effect of the convection by simplifying the melt flow as a constant horizontal flow. In this work, four convection behaviors, including equally distributed convection, linearly distributed convection, sinusoidal-wave convection, and square-wave convection, are imposed and simulated through the phase-field lattice-Boltzmann schemes. The effects of constant (the former two) and altering (the latter two) flow fields are quantified by the length ratio of the upstream primary arm to the downstream one. The results show that the dendrite asymmetry increases under the constant forced convections but presents nonmonotonic change under the altering convections. A simple mathematical relation is fitted to summarize the dependence of the dendrite asymmetry on the input velocity, the undercooling, and the flow frequency. Deep understanding of the convection effects can guide the prediction and control of the magnesium dendrite under more complex situations. Full article

The heterogeneity of concrete is a major challenge for acoustic emission monitoring. A method of active-passive joint acoustic emission monitoring considering the heterogeneity of concrete is presented herein, and the time-frequency-space multi-parameter response characteristics of active and passive acoustic emission signals were studied in relation to the damage evolution of concrete. This method provides an idea of evaluating the damage state of concrete more actively and quantitatively than traditional methods. The results show that the microscopic damage model of concrete based on the acoustic emission penetrating wave velocity and amplitude is in agreement with the damage process of concrete. The standard deviation of the wave velocity up to 1000 m/s and the change rate of the amplitude up to −0.66 can be adopted as two signs that the load of concrete reached 70% of the ultimate load. The time-of-arrival localization based on variable velocity was used to correct the acoustic emission localization results, and the localization accuracy was increased by 44.74%. The damage process of concrete undergoes diverse changes; that is, the distribution of damage changes from heterogeneous to homogeneous and then back to heterogeneous. Hence, it is necessary for researchers to consider the heterogeneity of concrete when using acoustic emission monitoring. The active-passive joint acoustic emission monitoring is an effective method. Full article

Power electronics are becoming increasingly more important, as electrical energy constitutes 40% of the total primary energy usage in the USA and is expected to grow rapidly with the emergence of electric vehicles, renewable energy generation, and energy storage. New materials that are better suited for high-power applications are needed as the Si material limit is reached. Beta-phase gallium oxide (β-Ga₂O₃) is a promising ultra-wide-bandgap (UWBG) semiconductor for high-power and RF electronics due to its bandgap of 4.9 eV, large theoretical breakdown electric field of 8 MV cm⁻¹, and Baliga figure of merit of 3300, 3–10 times larger than that of SiC and GaN. Moreover, β-Ga₂O₃ is the only WBG material that can be grown from melt, making large, high-quality, dopable substrates at low costs feasible. Significant efforts in the high-quality epitaxial growth of β-Ga₂O₃ and β-(Al_xGa_1−x)₂O₃ heterostructures has led to high-performance devices for high-power and RF applications. In this report, we provide a comprehensive summary of the progress in β-Ga₂O₃ field-effect transistors (FETs) including a variety of transistor designs, channel materials, ohmic contact formations and improvements, gate dielectrics, and fabrication processes. Additionally, novel structures proposed through simulations and not yet realized in β-Ga₂O₃ are presented. Main issues such as defect characterization methods and relevant material preparation, thermal studies and management, and the lack of p-type doping with investigated alternatives are also discussed. Finally, major strategies and outlooks for commercial use will be outlined. Full article

In recent times, ion implantation has received increasing interest for novel applications related to deterministic material doping on the nanoscale, primarily for the fabrication of solid-state quantum devices. For such applications, precise information concerning the number of implanted ions and their final position within the implanted sample is crucial. In this work, we present an innovative method for the detection of single ions of MeV energy by using a sub-micrometer ultra-thin silicon carbide sensor operated as an in-beam counter of transmitted ions. The SiC sensor signals, when compared to a Passivated Implanted Planar Silicon detector signal, exhibited a 96.5% ion-detection confidence, demonstrating that the membrane sensors can be utilized for high-fidelity ion counting. Furthermore, we assessed the angular straggling of transmitted ions due to the interaction with the SiC sensor, employing the scanning knife-edge method of a focused ion microbeam. The lateral dimension of the ion beam with and without the membrane sensor was compared to the SRIM calculations. The results were used to discuss the potential of such experimental geometry in deterministic ion-implantation schemes as well as other applications. Full article

The aim of this study was to investigate the low-temperature degradation (LTD) kinetics of tetragonal zirconia with 3 mol% yttria (3Y-TZP) dental ceramic using two degradation methods: hydrothermal degradation and immersed degradation. To study transformation kinetics, we prepared 3Y-TZP powders. We pressed these powders uniaxially into a stainless mold at 100 MPa. We then sintered the compacted bodies at intervals of 50 °C between 1300 °C and 1550 °C and immersed the specimens at various temperatures from 60 °C to 80 °C in 4% acetic acid or from 110 °C to 140 °C for the hydrothermal method. We used a scanning electron microscope (SEM) to confirm crystalline grain size and used X-ray diffraction to analyze the zirconia phase. As the sintering temperature increased, the calculated crystalline grain size also increased. We confirmed this change with the SEM image. The higher sintering temperatures were associated with more phase transformation. According to the Mehl–Avrami–Johnson equation, the activation energies achieved using the hydrothermal method were 101 kJ/mol, 95 kJ/mol, and 86 kJ/mol at sintering temperatures of 1450 °C, 1500 °C, and 1550 °C, respectively. In addition, the activation energies of the specimens immersed in 4% acetic acid were 60 kJ/mol, 55 kJ/mol, 48 kJ/mol, and 35 kJ/mol, with sintered temperatures of 1400 °C, 1450 °C, 1500 °C, and 1550 °C, respectively. The results showed that a lower sintering temperature would restrain the phase transformation of zirconia because of the smaller crystalline grain size. As a result, the rate of LTD decreased. Full article

This study investigates the mixed-mode I/II fracture behavior of O-notched diagonally loaded square plate (DLSP) samples containing an edge crack within the O-notch. This investigation aims to explore the combined effects of loading rate and mode mixity on the fracture properties of steel 304L, utilizing DLSP samples. The DLSP samples, made from strain-hardening steel 304L, were tested at three different loading rates: 1, 50, and 400 mm/min, covering five mode mixities from pure mode I to pure mode II. Additionally, tensile tests were performed on dumbbell-shaped specimens at the same loading rates to examine their influence on the material’s mechanical properties. The findings revealed that stress and strain diagrams derived from the dumbbell-shaped samples were largely independent of the tested loading rates (i.e., 1–400 mm/min). Furthermore, experimental results from DLSP samples showed no significant impact of the loading rates on the maximum load values, but did indicate an increase in the ultimate displacement. In contrast to the loading rate, mode mixity exhibited a notable effect on the fracture behavior of DLSP samples. Ultimately, it was observed that the loading rate had an insignificant effect on the fracture path or trajectory of the tested DLSP samples. Full article

The evaluation of the technical condition of historic buildings that have operated for several hundred years is a complicated issue. Even buildings that are in very poor condition must be checked and assessed in terms of their further repair, strengthening, or compliance with conditions that allow the facility to be safely operated. Most 18th-century buildings have not survived to this day retaining their original arrangements and structural elements. Renovations and repair work in the past were often carried out using materials of uncertain quality, with repair work of different qualities and without detailed analysis or methodology, based only on the experience of the former builders. In historic structures, the character of the work of individual structural elements has often changed due to significant material degradation, the poor quality of repair work, or the loss of adequate support. When load transfers change, internal forces are redistributed, and, as a result, the static scheme changes. This article presents an overview of identified defects affecting the change in static schemes in historical building structures built in the 18th century, using the example of a historic building with a large number of aforementioned defects. The process of assessing the technical condition of the facility is presented, in which non-destructive testing (NDT) methods were used. Detailed computational analyses were carried out for the wooden roof truss structure, which had partially lost its support. Full article

A hierarchical hybrid coating (HHC) comprising a ceramic oxide layer and two biodegradable polymeric (polycaprolactone, PCL) layers has been developed on Mg3Zn0.4Ca cast alloy in order to provide a controlled degradation rate and functionality by creating a favorable porous surface topography for cell adhesion. The inner, ceramic layer formed by plasma electrolytic oxidation (PEO) has been enriched in bioactive elements (Ca, P, Si). The intermediate PCL layer sealed the defect in the PEO layer and the outer microporous PCL layer loaded with the appropriate active molecule, thus providing drug-eluting capacity. Morphological, chemical, and biological characterizations of the manufactured coatings loaded with ciprofloxacin (CIP) and paracetamol (PAR) have been carried out. In vitro assays with cell lines relevant for cardiovascular implants and bone prosthesis (endothelial cells and premyoblasts) showed that the drug-loaded coating allows for cell proliferation and viability. The study of CIP and PAR cytotoxicity and release rate indicated that the porous PCL layer does not release concentrations detrimental to the cells. However, complete system assays revealed that corrosion behavior and increase of the pH negatively affects cell viability. H₂ evolution during corrosion of Mg alloy substrate generates blisters in PCL layer that accelerate the corrosion locally in crevice microenvironment. A detailed mechanism of the system degradation is disclosed. The accelerated degradation of the developed system may present interest for its further adaptation to new cancer therapy strategies. Full article

The so-called population balance model (PBM) is the most widely used approach to describe the grinding process. The analysis of the grinding data is carried out using—among others—the one-size fraction BII method. According to the BII method, the breakage parameters can be determined when a narrow particle size fraction is used as feed material to the mill. However, it is commonly accepted that these parameters are influenced by changing the particle size distribution in the mill. Thus, this study examines the breakage parameters through kinetic testing in different natural-size distribution environments generated by closed-cycle grinding tests that simulate industrial milling conditions. The differentiation of the milling environments was accomplished using various reference sieves in the closed-cycle tests. The experimentally determined breakage parameters were back-calculated and then used to simulate the closed-cycle tests using the MODSIM^TM software. Additionally, the energy efficiency was evaluated based on the specific surface area of the grinding products and the energy consumption. The results of the kinetic tests showed that the breakage rate of the coarse particles increases as the aperture size of the reference sieve decreases, and consequently, the content of fines in the mill increases. The back-calculated breakage parameters can be reliably used to simulate closed-cycle circuits, thus helping control industrial milling operations. Full article

Carbon dots (CDs) doped with heteroatoms have garnered significant interest due to their chemically modifiable luminescence properties. Herein, nitrogen- and sulfur-codoped carbon dots (NS-CDs) were successfully prepared using p-phenylenediamine and thioacetamide via a facile process. The as-developed NS-CDs had high photostability against photobleaching, good water dispersibility, and excitation-independent spectral emission properties due to the abundant amino and sulfur functional groups on their surface. The wine-red-colored NS-CDs exhibited strong green emission with a large Stokes shift of up to 125 nm upon the excitation wavelength of 375 nm, with a high quantum yield (QY) of 28%. The novel NS-CDs revealed excellent sensitivity for quercetin (QT) detection via the fluorescence quenching effect, with a low detection limit of 17.3 nM within the linear range of 0–29.7 μM. The fluorescence was quenched only when QT was brought near the NS-CDs. This QT-induced quenching occurred through the strong inner filter effect (IFE) and the complex bound state formed between the ground-state QT and excited-state NS-CDs. The quenching-based detection strategies also demonstrated good specificity for QT over various interferents (phenols, biomolecules, amino acids, metal ions, and flavonoids). Moreover, this approach could be effectively applied to the quantitative detection of QT (with good sensing recovery) in real food samples such as red wine and onion samples. The present work, consequently, suggests that NS-CDs may open the door to the sensitive and specific detection of QT in food samples in a cost-effective and straightforward manner. Full article

Composites consisting of iron aluminide and iron silicide phases were studied in this work. Powders of iron aluminide and iron silicide were prepared by mechanical alloying separately. Subsequently, they were blended in three different proportions and sintered by the SPS method under various conditions. After sintering, the composites are composed of FeAl and amounts of other silicides (Fe₅Si₃ and Fe₃Si). Ternary Fe–Al–Si phases were not determined, even though their presence was predicted by DFT calculations. This disagreement was explained by steric factors, i.e., by differences in the space lattice of the present phases. Hardness and tribological properties were measured on composites with various weight ratios of iron aluminide and iron silicide. The results show that sintered silicides with the matrix composed of iron aluminide reach comparable hardness to tool steels. The composites with higher mass ratios of iron aluminide than silicide have higher hardness and better tribological properties. Full article

Single-photon sources (SPSs) play a crucial role in quantum photonics, and colloidal quantum dots (CQDs) have emerged as promising and cost-effective candidates for such applications due to their high-purity single-photon emission at room temperature. This review focuses on various aspects of CQDs as SPSs. Firstly, a brief overview of the fundamental optical properties of CQDs is provided, including emission wavelength engineering and fluorescence intermittency, and their single-photon emission properties. Subsequently, this review delves into research concerning CQDs as SPSs, covering topics such as the coupling of single CQDs to microcavities, both in weak and strong coupling regimes. Additionally, methods for localizing and positioning CQDs are explored, which are critical for on-chip SPSs devices. Full article

The artificial neural networks (ANNs)-based model has been used to predict the compressive strength of concrete, assisting in creating recycled aggregate concrete mixtures and reducing the environmental impact of the construction industry. Thus, the present study examines the effects of the training algorithm, topology, and activation function on the predictive accuracy of ANN when determining the compressive strength of recycled aggregate concrete. An experimental database of compressive strength with 721 samples was defined considering the literature. The database was used to train, validate, and test the ANN-based models. Altogether, 240 ANNs were trained, defined by combining three training algorithms, two activation functions, and topologies with a hidden layer containing 1–40 neurons. The ANN with a single hidden layer including 28 neurons, trained with the Levenberg–Marquardt algorithm and the hyperbolic tangent function, achieved the best level of accuracy, with a coefficient of determination equal to 0.909 and a mean absolute percentage error equal to 6.81%. Furthermore, the results show that it is crucial to avoid the use of overly complex models. Excessive neurons can lead to exceptional performance during training but poor predictive ability during testing. Full article

The result of the development of additive manufacturing (AM) methods is the increasing use of the selective laser melting (SLM) method as a technique for producing tooling for injection moulds and die casting pressure moulds from maraging steel powders. The mould components are subjected to varying thermo-mechanical loads during these operations. This paper presents a numerical model that is used to predict the fatigue life of a material that is loaded with a time-varying temperature field according to the classic and modified Coffin test. Using a computational model, the temperature changes in the resistance-heated specimen and the stress and strain fields that are caused by this phenomenon were determined. Using three different multiaxial fatigue criteria, the fatigue life of SLM steel was determined. Numerical calculations were verified using experimental thermal fatigue tests on 1.2709 SLM steel that was aged at 490 °C as well as via metallographic tests. The numerical model was used to predict the durability of the same steel aged at 540 °C. The effect of specimen clamping conditions on the fatigue life of SLM steel was determined numerically. The value of the decrease in strength of SLM steel as a result of the increasing number of cycles of temperature changes was determined experimentally; a great influence of ageing temperature on fatigue life was found. Changes in the structure of steel occurring during cyclic changes in temperature are presented. Full article

This study aims to bridge various diagnostic tools for the development of smart plasma electrolytic oxidation (PEO) technologies. PEO treatments of commercially pure Zr were carried out using the pulsed unipolar polarisation (PUP) regime with frequency sweep in an alkaline phosphate-silicate electrolyte. Methods of in situ impedance spectroscopy and electrical transient analysis were used for the process diagnostics under the video imaging of the PEO. Two cutoff frequencies, 170–190 Hz and 620–650 Hz, were identified for the PEO-assisted charge transfer process. An equivalent circuit for the metal–oxide–electrolyte system under PUP PEO conditions was developed; from the capacitance values, two geometrical dielectric barriers were evaluated: a thinner 0.5–1 µm inner layer of the coating and a thicker 4–6 µm outer layer. These estimates were in agreement with the coating cross-sectional morphology. Based on comparing the results obtained using different techniques, the frequencies at which the uniform coatings with the best protective properties were formed were identified. For the selected electrolyte system and polarisation regime, these frequencies ranged from 2 to 5 kHz where the overall circuit reactance was minimal; therefore, the power factor was as close to one as possible. This opens the possibilities for the optimization of the pulsed PEO process and online control of unobservable surface characteristics, e.g., the thickness of the coating layers, thus contributing towards the development of smart PEO technologies. Full article

Two-dimensional nanomaterials have obvious advantages in thermoelectric device development. It is rare to use the same experimental system to accurately measure multiple thermoelectrical parameters of the same sample. Therefore, scholars have developed suspended microdevices, T-type and H-type methods to fulfill the abovementioned requirements. These methods usually require a direct-current voltage signal to detect in Seebeck coefficient measurement. However, the thermoelectric potential generated by the finite temperature difference is very weak and can be easily overwritten by the direct-current voltage, thereby affecting the measurement accuracy. In addition, these methods generally require specific electrodes to measure the thermoelectric potential. We propose a measurement method that combines laser heating with an H-type device. By introducing a temperature difference in two-dimensional materials through laser heating, the thermoelectric potential can be accurately measured. This method does not require specific electrodes to simplify the device structure. The thermoelectrical parameters of supported graphene are successfully measured with this method; the results are in good agreement with the literature. The proposed method is unaffected by material size and characteristics. It has potential application value in the characterization of thermoelectric physical properties. Full article

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm³⁺ and Tm³⁺/Ho³⁺ layer profiles. The low alumina content (Al₂O₃: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm₂O₃: 0.18wt % and Ho₂O₃: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55–2.10 µm). The calculated LP₀₁ Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs. Full article

In this study, 1T phase MoS₂ nanosheets were synthesized on the surface of a carbon cloth via a hydrothermal reaction. After heat treatment, the 1T phase MoS₂ was transformed into the 2H phase with a better capacity retention performance. As an anode material for lithium-ion batteries, 2H phase MoS₂ on the carbon cloth surface delivers a capacity of 1075 mAh g⁻¹ at a current density of 0.1 A g⁻¹ after 50 cycles; while the capacity of the 1T phase MoS₂ on the surface of the carbon cloth without heat treatment fades to 528 mAh g⁻¹. The good conductivity of a carbon cloth substrate and the separated MoS₂ nanosheets help to increase the capacity of MoS₂ and decrease its charge transfer resistance and promote the diffusion of lithium ions in the electrode. Full article