Search Results (905)

TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it forms a porous oxide film predominantly composed of TiO₂, which fails to provide adequate protection. Applying high-temperature protective coatings is therefore essential. Oxides demonstrating protective efficacy at elevated temperatures include Al₂O₃, Cr₂O₃, and SiO₂. The Pilling–Bedworth Ratio (PBR)—defined as the ratio of the volume of the oxide formed to the volume of the metal consumed—serves as a critical criterion for assessing oxide film integrity. A PBR value greater than 1 but less than 2 indicates superior film integrity and enhanced oxidation resistance. Among common oxides, Al₂O₃ exhibits a PBR value within this optimal range (1−2), rendering aluminum-based compound coatings the most extensively utilized. Aluminum coatings can be applied via methods such as pack cementation, thermal spraying, and hot-dip aluminizing. Pack cementation, being the simplest to operate, is widely employed. In this study, a powder mixture with the composition Al:Al₂O₃:NH₄Cl:CeO₂ = 30:66:3:1 was used to aluminize γ-TiAl intermetallic compound specimens via pack cementation at 600 °C for 5 h. Subsequent isothermal oxidation at 900 °C for 20 h yielded an oxidation kinetic curve adhering to the parabolic rate law. This treatment significantly enhanced the high-temperature oxidation resistance of the γ-TiAl intermetallic compound, thereby broadening its potential application scenarios. Full article

High-performance hydrogen gas sensors have gained considerable interest for their crucial function in reducing H₂ explosion risk. Although MoS₂ has good potential for chemical sensing, its application in hydrogen detection at room temperature is limited by slow response and incomplete recovery. In this work, Pd-doped MoS₂ thin films are deposited on a Si substrate, forming Pd-doped MoS₂/Si heterojunctions via magnetron co-sputtering. The incorporation of Pd nanoparticles significantly enhances the catalytic activity for hydrogen adsorption and facilitates more efficient electron transfer. Owing to its distinct structural characteristics and sharp interface properties, the fabricated Pd-doped MoS₂/Si heterojunction device exhibits excellent H₂ sensing performance under room temperature conditions. The gas sensor device achieves an impressive sensing response of ~6.4 × 10³% under 10,000 ppm H₂ concentration, representing a 110% improvement compared to pristine MoS₂. Furthermore, the fabricated heterojunction device demonstrates rapid response and recovery times (24.6/12.2 s), excellent repeatability, strong humidity resistance, and a ppb-level detection limit. These results demonstrate the promising application prospects of Pd-doped MoS₂/Si heterojunctions in the development of advanced gas sensing devices. Full article

During the last few years, the requirements for highly efficient, sustainable, and versatile materials in modern biomedicine, aircraft and aerospace industries, automotive production, and electronic and electrical engineering applications have increased. This has led to the development of new and innovative methods for material modification and optimization. This can be achieved in many different ways, but one such approach is the application of surface thin films. They can be conductive (metallic), semi-conductive (metal-ceramic), or isolating (polymeric). Special emphasis is placed on applying semi-conductive thin films due to their unique properties, be it electrical, chemical, mechanical, or other. The particular thin films of interest are composite ones of the type of transition metal oxide (TMO) and transition metal nitride (TMN), due to their widespread configurations and applications. Regardless of the countless number of studies regarding the application of such films in the aforementioned industrial fields, some further possible investigations are necessary to find optimal solutions for modern problems in this topic. One such problem is the possibility of characterization of the applied thin films, not via textbook approaches, but through a simple, modern solution using their electrical properties. This can be achieved on the basis of measuring the films’ electrical impedance, since all different semi-conductive materials have different impedance values. However, this is a huge practical work that necessitates the collection of a large pool of data and needs to be based on well-established methods for both characterization and formation of the films. A thorough review on the topic of applying thin films using physical vapor deposition techniques (PVD) in the field of different modern applications, and the current results of such investigations are presented. Furthermore, current research regarding the possible methods for applying such films, and the specifics behind them, need to be summarized. Due to this, in the present work, the specifics of applying thin films using PVD methods and their expected structure and properties were evaluated. Special emphasis was paid to the electrical impedance spectroscopy (EIS) method, which is typically used for the investigation and characterization of electrical systems. This method has increased in popularity over the last few years, and its applicability in the characterization of electrical systems that include thin films formed using PVD methods was proven many times over. However, a still lingering question is the applicability of this method for backwards engineering of thin films. Currently, the EIS method is used in combination with traditional techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and others. There is, however, a potential to predict the structure and properties of thin films using purely a combination of EIS measurements and complex theoretical models. The current progress in the development of the EIS measurement method was described in the present work, and the trend is such that new theoretical models and new practical testing knowledge was obtained that help implement the method in the field of thin films characterization. Regardless of this progress, much more future work was found to be necessary, in particular, practical measurements (real data) of a large variety of films, in order to build the composition–structure–properties relationship. Full article

Organic polymer introduction effectively enhances the toughness, bond strength, and durability of ordinary cement-based materials, and is often used for concrete repair and reinforcement. However, the entrained air effect simultaneously induced by polymer and the inhibitory action on cement hydration kinetics often lead to degradation in mechanical performances of polymer-modified cement-based composite (PMC). Nanomaterials provide unique advantages in enhancing the properties of PMC due to their characteristic ultrahigh specific surface area, quantum effects, and interface modulation capabilities. This review systematically examines recent advances in nano-reinforced PMC (NPMC), elucidating their synergistic optimization mechanisms. The synergistic effects of nanomaterials—nano-nucleation, pore-filling, and templating mechanisms—refine the microstructure, significantly enhancing the mechanical strength, impermeability, and erosion resistance of NPMC. Furthermore, nanomaterials establish interpenetrating network structures (A composite structure composed of polymer networks and other materials interwoven with each other) with polymer cured film (The film formed after the polymer loses water), enhancing load-transfer efficiency through physical and chemical action while optimizing dispersion and compatibility of nanomaterials and polymers. By systematically analyzing the synergy among nanomaterials, polymer, and cement matrix, this work provides valuable insights for advancing high-performance repair materials. Full article

Per- and polyfluoroalkyl substances (PFAS) have been reported to contaminate soil as a result of improper management of waste, wastewater, landfill leachate, biosolids, and a large and indiscriminate use of aqueous film-forming foams (AFFF), posing potential risks to human health. However, their high chemical and thermal stability pose a great challenge for remediation. As a result, there is an increasing interest in identifying and optimizing very effective and sustainable technologies for PFAS removal. This review summarizes both traditional and innovative remediation strategies and technologies for PFAS-contaminated soils. Unlike existing literature, which primarily focuses on the effectiveness of PFAS remediation, this review critically discusses several techniques (based on PFAS immobilization, mobilization and extraction, and destruction) with a deep focus on their sustainability and scalability. PFAS destruction technologies demonstrate the highest removal efficiencies; however, thermal treatments face sustainability challenges due to high energy demands and potential formation of harmful by-products, while mechanical treatments have rarely been explored at full scale. PFAS immobilization techniques are less costly than destruction methods, but issues related to the regeneration/disposal of spent sorbents should be still addressed and more long-term studies conducted. PFAS mobilization techniques such as soil washing/flushing are hindered by the generation of PFAS-laden wastewater requiring further treatments, while phytoremediation is limited to small- or medium-scale experiments. Finally, bioremediation would be the cheapest and least impactful alternative, though its efficacy remains uncertain and demonstrated under simplified lab-scale conditions. Future research should prioritize pilot- and full-scale studies under realistic conditions, alongside comprehensive assessments of environmental impacts and economic feasibility. Full article

Recently, with the development of automation technology in various fields, much research has been conducted on infrared photodetectors, which are the core technology of LiDAR sensors. However, most infrared photodetectors are expensive because they use compound semiconductors based on epitaxial processes, and they have low safety because they use the near-infrared (NIR) region that can damage the retina. Therefore, they are difficult to apply to automation technologies such as automobiles and factories where humans can be constantly exposed. In contrast, short-wavelength infrared photodetectors based on PbS QDs are actively being developed because they can absorb infrared rays in the eye-safe region by controlling the particle size of QDs and can be easily and inexpensively manufactured through a solution process. However, PbS QDs-based SWIR photodetectors have low chemical stability due to the electron/hole extraction layer processed by the solution process, making it difficult to manufacture them in the form of patterning and arrays. In this study, bulk NiO and ZnO were deposited by sputtering to achieve uniformity and patterning of thin films, and the performance of PbS QDs-based photodetectors was improved by optimizing the thickness and annealing conditions of the thin films. The fabricated photodetector achieved a high response characteristic of 114.3% through optimized band gap and improved transmittance characteristics. Full article

In the field of mechanical motion, friction loss and material wear are common problems. As one of the essential components for enhancing the lubricating performance of gel-like lubricants, nano-additives leverage their unique physical and chemical properties to form an efficient protective film on friction surfaces. This effectively reduces friction resistance and inhibits wear progression, thereby playing a significant role in promoting energy conservation, emissions reduction, and the implementation of green development principles. This study first introduces the physical and chemical preparation processes of gel-like lubricant nanoadditives. It then classifies them (mainly based on metal bases, metal oxides, nanocarbon materials, and other nanoadditives). Then, the performance of gel-like lubricant nano-additives is evaluated (mainly in terms of anti-wear, friction reduction, oxidation resistance, and load carrying capacity), and the surface analysis technology used is described. Finally, we summarize the application scenarios of gel-like lubricant nano-additives, identify the challenges faced, and discuss future prospects. This study provides new insights and directions for the design and synthesis of novel gel-like lubricants with significant lubricating and anti-wear properties in the future. Full article

Mesoporous silicon dioxide films have been shown to be well suited as adhesion-promoting interlayers for generating high-strength polymer–metal interfaces. These films can be fabricated via microwave plasma-enhanced chemical vapor deposition using the precursor hexamethyldisiloxane and oxygen as working gas. The resulting mesoporous structures enable polymer infiltration during overmolding, which leads to a nanoscale form-locking mechanism after solidification. This mechanism allows for efficient stress transfer across the interface and makes the resulting adhesion highly dependent on the morphology of the deposited film. To gain a deeper understanding of the underlying deposition mechanisms and improve process stability, this work investigates the growth behavior of mesoporous silica films using a multiple regression analysis approach. The seven process parameters coating time, distance, chamber pressure, substrate temperature, flow rate, plasma pulse duration, and pause-to-pulse ratio were systematically varied within a Design of Experiments framework. The resulting films were characterized by their free surface area, mean agglomerate diameter, and film thickness using digital image analysis, white light interferometry, and atomic force microscopy. The deposited films exhibit a wide range of morphological appearances, ranging from quasi-dense to dust-like structures. As part of this research, the free surface area varied from 15 to 55 percent, the mean agglomerate diameter from 17 to 126 nm, and the film thickness from 35 to 1600 nm. The derived growth model describes the deposition process with high statistical accuracy. Furthermore, all coatings were overmolded via injection molding and subjected to mechanical testing, allowing a direct correlation between film morphology and their performance as adhesion-promoting interlayers. Full article

Cardiovascular diseases are responsible for a large number of severe disability cases and deaths worldwide. Strong research in this field has been extensively carried out, in particular for the associated complications, such as the occlusion of small-diameter (<6 mm) vessels. Accordingly, in the present research, two random copolyesters of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(butylene isophthalate) (PBI), were successfully synthesized via two-step melt polycondensation and were thoroughly characterized from molecular, thermal, and mechanical perspectives. The copolymeric films displayed a peculiar thermal behavior, being easily processable in the form of films, although amorphous, with T_g close to room temperature. Their thermal stability was high in all cases, and from the mechanical point of view, the materials exhibited a high ultimate strength, together with values of elastic moduli tunable with the chemical composition. The long-term stability of these materials under physiological conditions was also demonstrated. Cytotoxicity was assessed using a direct contact assay with human umbilical vein endothelial cells (HUVECs). In addition, hemocompatibility was tested by evaluating the adhesion of blood components (such as the adsorption of human platelets and fibrinogen). As a result, a proper chemical design and, in turn, both the solid-state and functional properties, are pivotal in regulating cell behavior and opening new frontiers in the tissue engineering of soft tissues, including vascular tissues. Full article

This study synthesized two eco-friendly inhibitors—a chitosan–copper metal–organic framework (CS@Cu MOF) and chitosan–Schiff base–Cu complex (Schiff–CS@Cu)—for Q345 steel protection in 3.5% NaCl/1M HCl. Electrochemical and weight loss analyses demonstrated exceptional corrosion inhibition: untreated specimens showed a 25.889 g/(m²·h) corrosion rate, while 100 mg/L of CS@Cu MOF and Schiff–CS@Cu reduced rates to 2.50 g/(m²·h) (90.34% efficiency) and 1.67 g/(m²·h) (93.56%), respectively. Schiff–CS@Cu’s superiority stemmed from its pyridine–Cu²⁺ chelation forming a dense coordination barrier that impeded Cl⁻/H⁺ penetration, whereas CS@Cu MOF relied on physical adsorption and micro-galvanic interactions. Surface characterization revealed that Schiff–CS@Cu suppressed pitting nucleation through chemical coordination, contrasting with CS@Cu MOF’s porous film delaying uniform corrosion. Both inhibitors achieved optimal performance at 100 mg/L concentration. This work establishes a molecular design strategy for green inhibitors, combining metal–organic coordination chemistry with biopolymer modification, offering practical solutions for marine infrastructure and acid-processing equipment protection. Full article

We present the results of silicon carbide (SiC) thin film synthesis on Si(111) substrates using chemical vapor deposition by decomposing CH₄ in H₂ at 1135 °C. The experiments were conducted in an Oxford Nanofab Plasmalab System 100 for carbon phase deposition times of 3, 5, 20, 60, and 90 min on Si(111) with or without native oxide, following established protocols. Our studies show that either predominantly crystalline SiC or a mixture of SiC and Si–O/Si–O–C glass forms on Si substrates significantly doped with carbon and oxygen, depending on the presence or absence of native oxide. The thickness of the SiC film ranges from approximately 5–6 nm for films synthesized in 3 min to over 15 nm for those synthesized in 90 min, while the size of the crystal grains varies from a few to 110 nm depending on the synthesis duration. The findings suggest that the complex composition of the thin films and the region beneath them can more effectively compensate for the differences in lattice parameters and thermal expansion coefficients between the SiC film and the Si substrate; thus, this method is promising for depositing intermediate thin films of SiC on Si substrates. Full article

This study investigates the development and sensing profile of synthetic melanin nanoparticle-coated electrodes for the electrochemical detection of heavy metals, including lead (Pb), cadmium (Cd), cobalt (Co), zinc (Zn), nickel (Ni), and iron (Fe). Synthetic melanin films were prepared in situ by the deacetylation of diacetoxy indole (DAI) to dihydroxy indole (DHI), followed by the deposition of DHI monomers onto indium tin oxide (ITO) and glassy carbon electrodes (GCE) using cyclic voltammetry (CV), forming a thin layer of synthetic melanin film. The deposition process was characterized by electrochemical quartz crystal microbalance (EQCM) in combination with linear sweep voltammetry (LSV) and amperometry to determine the mass and thickness of the deposited film. Surface morphology and elemental composition were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). In contrast, Fourier-transform infrared (FTIR) and UV–Vis spectroscopy confirmed the melanin’s chemical structure and its polyphenolic functional groups. Differential pulse voltammetry (DPV) and amperometry were employed to evaluate the melanin films’ electrochemical activity and sensitivity for detecting heavy metal ions. Reproducibility and repeatability were rigorously assessed, showing consistent electrochemical performance across multiple electrodes and trials. A comparative analysis of ITO, GCE, and graphite electrodes was conducted to identify the most suitable substrate for melanin film preparation, focusing on stability, electrochemical response, and metal ion sensing efficiency. Finally, the applicability of melanin-coated electrodes was tested on in-house heavy metal water samples, exploring their potential for practical environmental monitoring of toxic heavy metals. The findings highlight synthetic melanin-coated electrodes as a promising platform for sensitive and reliable detection of iron with a sensitivity of 106 nA/ppm and a limit of quantification as low as 1 ppm. Full article

Se-doped CdTe thin films were grown employing a simple two-electrode electrochemical deposition method using glass/tin-doped indium oxide (glass/ITO). Cadmium acetate dihydrate [Cd (CH₃CO₂)₂. 2H₂O], selenium dioxide (SeO₂), and tellurium dioxide (TeO₂) were used as precursors. Instruments including X-ray diffraction for structural investigation, UV-Vis spectrophotometry for optical properties, and scanning probe microscopy for morphological properties were employed to investigate the physico-chemical characteristics of the resulting Se-doped CdTe thin-film. The films are polycrystalline with a cubic phase, according to X-ray diffraction (XRD) data. More ions are deposited on the substrate, which makes the material more crystalline and intensifies the characteristic peaks that are seen. It is observed from the acquired optical characterization that the film’s bandgap is greatly influenced by the deposition time. The bandgap dropped from 1.92 to 1.62 as the deposition period increased from 25 to 45 min, making the film more transparent and absorbing less light at shorter deposition durations. Images from scanning electron microscopy (SEM) show that the surface morphology is homogenous with closely packed grains and that the grain forms become less noticeable as the deposition time increases. This work is novel in that it investigates the influence of the deposition time on the structural, optical, and morphological properties of Se-doped CdTe thin films deposited using a cost-effective, simplified two-electrode electrochemical method—a fabrication route that remains largely unexplored for this material system. Full article

Over the last decade, polymeric carbon nitrides (PCNs) have received exponentially growing attention as metal-free photocatalytic platforms for green energy generation and environmental remediation. Although PCNs can be easily synthesized from abundant precursors in a powdered form, progress in the field of photoelectrochemical applications requires effective methods for the fabrication of PCN films endowed with suitable mechanical stability and modular chemico-physical properties. In this context, as a proof-of-concept, we report herein on a simple and versatile chemical vapor infiltration (CVI) strategy for one-step PCN growth on porous Ni foam substrates, starting from melamine as a precursor compound. Interestingly, tailoring the reaction temperature enabled to control the condensation degree of PCN films from melem/melon hybrids to melon-like materials, whereas the use of different precursor amounts directly affected the mass and morphology of the obtained deposits. Altogether, such features had a remarkable influence on PCN electrochemical performances towards the oxygen evolution reaction (OER), yielding, for the best performing systems, Tafel slopes as low as ≈65 mV/dec and photocurrent density values of ≈1 mA/cm² at 1.6 V vs. the reversible hydrogen electrode (RHE). Full article

Graphene oxide (GO) films have attracted significant attention due to their potential in separation and filtration applications. Based on their unique lamellar structure and ultrathin nature, GO films are difficult to maintain in a free-standing form and typically require substrate support. Consequently, understanding their film formation behavior and mechanisms on substrates is of paramount importance. This work employs commonly used nonwoven fibrous membranes as substrates and guided by the coffee-ring theory, systematically investigates the film formation behaviors, film morphology, and underlying mechanisms of GO films on fibrous membranes with varying wettability. Fibrous membranes with different wetting properties—hydrophilic, hydrophobic, and superhydrophobic—were prepared via electrospinning and initiated chemical vapor deposition (iCVD) surface modification techniques. The spreading behaviors, deposition dynamics, capillary effects, and evaporation-induced film formation mechanisms of GO suspensions on these substrates were thoroughly examined. The results showed that GO formed belt-like, ring-like, and circular patterns on the three fibrous membranes, respectively. GO films encapsulated more than the upper half, approximately the upper half, and the top portion of fibers, respectively. Pronounced wrinkling of GO films was observed except for those on the hydrophilic fibrous membrane. This work demonstrates that tuning the wettability of fibrous substrates enables precise control over GO film morphology, including fiber encapsulation, wrinkling, and coverage area. Furthermore, it deepens the understanding of the interactions between 1D nanofibers and 2D GO sheets at low-dimensional scales, laying a foundational basis for the optimized design of membrane engineering. Full article