Search Results (152)

In this work, hybrid membranes were fabricated by depositing polyvinyl chloride (PVC) fibers onto PET track-etched membranes (TeMs) using the electrospinning technique. The resulting structures exhibited enhanced hydrophobicity, with contact angles reaching 155°, making them suitable for applications in both water–oil mixture separation and membrane distillation processes involving low-level liquid radioactive waste (LLLRW), saline solutions, and natural water sources. The use of hybrids of TeMs and nanofiber membranes has significantly increased productivity compared to TeMs only, while maintaining a high degree of purification. Permeate obtained after MD of LLLRW and river water was analyzed by conductometry and the atomic emission spectroscopy (for Sr, Cs, Al, Mo, Co, Sb, Ca, Fe, Mg, K, and Na). The activity of radioisotopes (for ¹²⁴Sb, ⁶⁵Zn, ⁶⁰Co, ⁵⁷Co, ¹³⁷Cs, and ¹³⁴Cs) was evaluated by gamma-ray spectroscopy. In most cases, the degree of rejection was between 95 and 100% with a water flux of up to 17.3 kg/m²·h. These membranes were also tested in the separation of cetane–water emulsion with productivity up to 47.3 L/m²·min at vacuum pressure of 700 mbar and 15.2 L/m²·min at vacuum pressure of 900 mbar. Full article

The rapid progress in additive manufacturing (AM) has unlocked significant possibilities for producing 316/316L stainless steel components, particularly in industries requiring high precision, enhanced mechanical properties, and intricate geometries. However, the widespread adoption of AM—specifically Directed energy deposition (DED), selective laser melting (SLM), and electron beam melting (EBM) remains challenged by inherent process-related defects such as residual stresses, porosity, anisotropy, and surface roughness. This review critically examines these AM techniques, focusing on optimizing key manufacturing parameters, mitigating defects, and implementing effective post-processing treatments. This review highlights how process parameters including laser power, energy density, scanning strategy, layer thickness, build orientation, and preheating conditions directly affect microstructural evolution, mechanical properties, and defect formation in AM-fabricated 316/316L stainless steel. Comparative analysis reveals that SLM excels in achieving refined microstructures and high precision, although it is prone to residual stress accumulation and porosity. DED, on the other hand, offers flexibility for large-scale manufacturing but struggles with surface finish and mechanical property consistency. EBM effectively reduces thermal-induced residual stresses due to its sustained high preheating temperatures (typically maintained between 700 °C and 850 °C throughout the build process) and vacuum environment, but it faces limitations related to resolution, cost-effectiveness, and material applicability. Additionally, this review aligns AM techniques with specific defect reduction strategies, emphasizing the importance of post-processing methods such as heat treatment and hot isostatic pressing (HIP). These approaches enhance structural integrity by refining microstructure, reducing residual stresses, and minimizing porosity. By providing a comprehensive framework that connects AM techniques optimization strategies, this review serves as a valuable resource for academic and industry professionals. It underscores the necessity of process standardization and real-time monitoring to improve the reliability and consistency of AM-produced 316/316L stainless steel components. A targeted approach to these challenges will be crucial in advancing AM technologies to meet the stringent performance requirements of various high-value industrial applications. Full article

The primary challenge associated with stainless steel in fuel cell operation is its susceptibility to corrosion, which leads to increased contact resistance and subsequent degradation of electrochemical performance. In general, the protective layers have been loaded onto the metal surface by widely used traditional techniques such as physical vapor deposition (PVD), or cathode arc ion plating. However, the above sputtering and evaporation ways require a high-vacuum condition, complicated experimental setups, higher costs, and an elevated temperature. Therefore, herein the achievement for uniform coatings over a large surface area has been realized by using a cost-effective strategy through a complete wet chemical process. The synergistic regulation of two conductive components and a plastic additive has been employed together with the entrapment of a surfactant to optimize the microstructure of the coating surface. The assembly of layered graphite and a polystyrene sphere could maintain both the high corrosion resistance feature and excellent electrical conductivity. In particular, the intrinsic vacant space in the above physical barriers has been filled with fine powders of indium tin oxide (ITO) due to its small size, and the interconnected conductive network with vertical/horizontal directions would be formed. All the key technical targets based on the U.S. Department of Energy (DOE) have been achieved under the simulated operating environments of a proton exchange membrane fuel cell. The corrosion current density has been measured as low as 0.52 μA/cm² (for the sample of graphite/mixed layer) over the applied potentials from −0.6 V to 1.2 V and its protective efficiency is evaluated to be 99.8%. The interfacial contact resistance between the sample and the carbon paper is much less than 10 mΩ·cm² (3.4 mΩ·cm²) under a contact pressure of 165 N/cm². The wettability has been investigated and its contact angle has been evolved from 48° (uncoated sample) to even 110°, providing superior hydrophobicity to prevent water penetration. Such an innovative approach opens up new possibilities for improving the durability and reducing the costs of carbon-based coatings. Full article

Transition metal dichalcogenides, especially molybdenum disulfide (MoS₂), exhibit exceptional properties that make them suitable for a wide range of applications. However, the interaction between MoS₂ and technologically relevant substrates, such as platinum (Pt) electrodes, can significantly influence its properties. This study investigates the growth and properties of MoS₂ thin films on Pt substrates using ionized jet deposition, a versatile, low-cost vacuum deposition technique. We explore the effects of the roughness of Pt substrates and self-heating during deposition on the chemical composition, structure, and strain of MoS₂ films. By optimizing the deposition system to achieve crystalline MoS₂ at room temperature, we compare as-deposited and annealed films. The results reveal that as-deposited MoS₂ films are initially amorphous and conform to the Pt substrate roughness, but crystalline growth is reached when the sample holder is sufficiently heated by the plasma. Further post-annealing at 270 °C enhances crystallinity and reduces sulfur-related defects. We also identify a change in the MoS₂–Pt interface properties, with a reduction in Pt–S interactions after annealing. Our findings contribute to the understanding of MoS₂ growth on Pt and provide insights for optimizing MoS₂-based devices in catalysis and electronics. Full article

Direct-writing submicron copper circuits on glass with laser precision—without lithography, vacuum deposition, or etching—represents a transformative step in next-generation microfabrication. We present a high-resolution, maskless method for metallizing glass using ultrashort pulse Bessel beam laser processing, followed by silver ion activation and electroless copper plating. The laser-modified glass surface hosts nanoscale chemical defects that promote the in situ reduction of Ag⁺ to metallic Ag⁰ upon exposure to AgNO₃ solution. These silver seeds act as robust catalytic and adhesion sites for subsequent copper growth. Using this approach, we demonstrate circuit traces as narrow as 0.7 µm, featuring excellent uniformity and adhesion. Compared to conventional redistribution-layer (RDL) and under-bump-metallization (UBM) techniques, this process eliminates multiple lithographic and vacuum-based steps, significantly reducing process complexity and production time. The method is scalable and adaptable for applications in transparent electronics, fan-out packaging, and high-density interconnects. Full article

In this work, the transport properties of charge carriers in $\beta$-Ga${}_2$O${}_3$ were investigated, along with intrinsic physical mechanisms such as lattice vibrations, impurity scattering, and interfacial effects. The high-field behavior of carrier mobility was characterized using vacuum deposition techniques for the fabrication of electrodes with ohmic contacts, and the Hall effect measurement system was employed to test the temperature-dependent mobility of Sn-doped n-type (100) and (001) $\beta$-Ga${}_2$O${}_3$ samples at a cryogenic temperature. A predictive model for $\beta$-Ga${}_2$O${}_3$ mobility was developed by examining the effects of the temperature on the scattering mechanisms based on a theoretical transport model. The experimental results for $\beta$-Ga${}_2$O${}_3$ mobility, which varied with the temperature and doping concentration, showed good agreement with the theoretical model within the temperature range of 15–300 K. The maximum discrepancy between the predictive model and the experimental data was less than 5%. This study provides valuable theoretical insights for the design and simulation of $\beta$-Ga${}_2$O${}_3$ devices. Full article

The original Glancing Angle Deposition (GLAD) technique was developed using the evaporation process, i.e., in high vacuum, with a nearly punctual source, and with the substrate aligned with the source axis. In this specific case, the substrate tilt angle can be assumed to be equal to the impinging incidence angle of evaporated atoms. With the sputtering process, the deposition pressure is higher, sources are larger, and substrates are not intrinsically aligned with the source. As a result, deviations from the growth models applied for evaporation are reported, and the substrate tilt angle is no longer relevant for describing the impinging atomic flux. To control the inclined nanostructure of metallic films, a relevant description of the atomic flux is required, applicable across all deposition configurations. In this work, transport simulation is used to determine the resultant incidence angle, a unique criterion relevant to each specific deposition condition. The different representations of the flux are described and discussed, and some typical examples of the resultant angles are presented. Ten elements are investigated: three hcp transition metals (Ti, Zr, and Hf), six bcc transition metals (V, Nb, Ta, Cr, Mo, and W), and one fcc post-transition metal (Al). Full article

Self-assembled monolayers (SAMs) have gained significant attention as an interfacial engineering strategy for perovskite solar cells (PSCs) due to their efficient charge transport ability and work function tunability. While solution-based methods such as dip-coating and spin-coating are widely used for SAM deposition, challenges such as non-uniform coverage, solvent contamination, and limited control over molecular orientation hinder their scalability and reproducibility. In contrast, vacuum deposition techniques, including thermal evaporation, overcome these limitations by enabling the formation of highly uniform materials with precise control over thickness and molecular arrangement. Importantly, the chemical interactions between SAM materials and perovskite layers, including coordination bonding with Pb²⁺ ions, play an important role in passivating surface defects, modulating energy levels, and promoting uniform perovskite crystallization. These interactions not only enhance wettability but also improve the overall quality and stability of perovskite films. This review highlights the advantages of vacuum-deposited SAMs, promoting strong chemical interactions with perovskite layers and improving interfacial properties critical for scalable applications. Full article

Structural batteries, also known as “massless batteries”, integrate energy storage directly into load-bearing materials, offering a transformative alternative to traditional Li-ion batteries. Unlike conventional systems that serve only as energy storage devices, structural batteries replace passive structural components, reducing overall weight while providing mechanical reinforcement. However, achieving uniform and efficient coatings of active materials on carbon fibers remains a major challenge, limiting their scalability and electrochemical performance. This study investigates ultrasonic spray coating as a precise and scalable technique for fabricating composite cathodes in structural batteries. Using a computer-controlled ultrasonic nozzle, this method ensures uniform deposition with minimal material waste while maintaining the mechanical integrity of carbon fibers. Compared to traditional techniques such as electrophoretic deposition, vacuum bag hot plate processing, and dip-coating, ultrasonic spray coating achieved superior coating consistency and reproducibility. Electrochemical testing revealed a specific capacity of 100 mAh/g_LFP with 80% retention for more than 350 cycles at 0.5 C, demonstrating its potential as a viable coating solution. While structural batteries are not yet commercially viable, these findings represent a step toward their practical implementation. Further research and optimization will be essential in advancing this technology for next-generation aerospace and transportation applications. Full article

Chemical vapor deposition (CVD) is a highly adaptable manufacturing technique used to fabricate high-quality thin films, making it essential across numerous industries. As materials fabrication processes progress, CVD has advanced to enable the precise deposition of both inorganic 2D materials, such as graphene and transition metal dichalcogenides, and high-quality polymeric thin films, offering excellent conformality and precise nanostructure control on a wide range of substrates. Conjugated conducting polymers have emerged as promising materials for next-generation electronic, optoelectronic, and energy storage devices due to their unique combination of electrical conductivity, optical transparency, ionic transport, and mechanical flexibility. Oxidative CVD (oCVD) involves the spontaneous reaction of oxidant and monomer vapors upon their adsorption onto the substrate surface, resulting in step-growth polymerization that commonly produces conducting or semiconducting polymer thin films. oCVD has gained significant attention for its ability to fabricate conjugated conducting polymers under vacuum conditions, allowing precise control over film thickness, doping levels, and nanostructure engineering. The low to moderate deposition temperature in the oCVD method enables the direct integration of conducting and semiconducting polymer thin films onto thermally sensitive substrates, including plants, paper, textiles, membranes, carbon fibers, and graphene. This review explores the fundamentals of the CVD process and vacuum-based manufacturing, while also highlighting recent advancements in the oCVD method for the fabrication of conjugated conducting and semiconducting polymer thin films. Full article

The present study reports the tribological properties and residual stress of titanium chromium nitride (TiCrN) coatings. Thin films of TiCrN were deposited on tungsten carbide substrates at 400 °C in a vacuum of 5 × 10⁻⁶ mbar using the cathodic-arc physical vapor deposition technique with chromium variation. X-ray diffraction (XRD) spectroscopy was employed to probe the structures of the deposited thin films. The phase constituent was found to gradually shift from cubic TiN to cubic CrN. Both the hardness and elastic modulus of the sheet changed from 29.7 to 30.9 GPa and 446 to 495 GPa, respectively. The biaxial compressive residual stress after an initial absolute scan in the range of 30–100° was determined using XRD (d-sin²ψ method). These mechanical and tribological properties of films were investigated with the help of instrumented nanoindentation and a ball-on-disk tribometer wear test. The wear test indicates that the TiCrN thin film, featuring a Cr/Ti ratio of 0.587, exhibits superior wear resistance and maximum compressive residual stress in comparison to other thin films. Full article

Ti-6Al-4V is a well-known alloy for its low density and excellent corrosion resistance, making it popular in aerospace, marine, medical, and automotive applications. However, at elevated temperatures, the alloy forms oxides, leading to embrittlement. In additive manufacturing, particularly in the direct energy deposition (DED) process, which involves high temperatures, the alloy experiences oxidation. An inert gas chamber provides shielding during the process but limits the size of the manufactured components, and deposition in a vacuum chamber can alter the chemical composition of the alloy. Local shielding is a technique generally used for such applications, but it uses a high volume of shield gas, contributing to environmental contamination. This study presents a novel approach for the development and preliminary evaluation of a prototype nozzle attachment system for the additive manufacturing (AM) of Ti-6Al-4V using a direct energy deposition (DED) process in an open-air environment system. The system was designed to reduce shield gas consumption by providing conformal shielding in critical areas. This was achieved by dividing the shielding area into eight segments, with each of the eight attachments of the nozzle attachment system selectively activated to supply shield gas only where required. Four different shield gas flow rates of 20, 25, 30, and 35 SCFH were tested at three different locations under the attachment to investigate the optimal flow rate. The results proposed maintaining a baseline flow rate of 5 SCFH in all attachments and employing 60 SCFH during transitions between attachments for rapid shielding. The system maintained oxygen concentration levels below 200 PPM within 2.1 s, with an average gas consumption of 65 SCFH, underlining an 85% reduction compared to other studies. These findings highlight the potential of this system for future implementation and scalability for reactive metal depositions like Ti-6Al-4V in AM using DED processes. This study addresses the need for an effective shielding environment during deposition while minimizing the shield gas consumption. A nozzle attachment system was designed and developed to provide conformal shielding during the deposition process. Key parameters, such as the shielding flow rate, activation time, and shielding range of the nozzle attachments, were investigated. The system successfully delivered shield gas to the critical areas and provided a safe environment for deposition. Argon consumption was reduced by 85% compared to other studies in the same field, with an optimal flow rate of 25 Standard Cubic Feet per Hour (SCFH) of shielding gas used to cover all critical areas in the experiments. The effect of the laminar and turbulent flow of shield gas on the deposition path was also analyzed in this study. Full article

The adsorption and reaction of nitric oxide (NO) molecules on the surface of the model-supported metal/oxide system, consisting of Ni nanoparticles deposited on α-Al₂O₃ (0001) in ultra-high vacuum, have been studied using in situ surface-sensitive techniques and density functional theory (DFT) calculations. As a combination of X-ray and Auger electron spectroscopy (XPS, AES), Fourier-transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) techniques reveals, there is a threshold of Ni particle mean size (<d>) of c.a. 2 nm, differentiating the electron state of adsorbed NO molecules and their reaction. The main feature of Ni particles normally not exceeding 2 nm is that the NO adsorbs in the form of (NO)₂ dimers, whereas, for larger particles, the NO molecules adsorb in the form of monomers, usually characteristic for the bulk Ni substrate. This difference is demonstrated to be the main reason for the different reaction of NO molecules on the surface of Ni/alumina. The striking feature is that, in the case of ultra-small Ni particles (<d> ≤ 2 nm), the nitrous oxide (N₂O) molecules are formed upon heating as a result of the NO self-reduction mechanism, which are otherwise not formed in the case of larger Ni particles. According to DFT results, this is due to the significant synergistic impact of NO co-adsorption on the neighboring NO dissociation reaction over ultra-small Ni particles, mediated by the metal/oxide perimeter interface. The observed molecular conversion effects offer an opportunity to tune the catalytic selectivity of this and related metal/oxide systems via varying the supported metal particle size. Full article

Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS₂ crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS₂ with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS₂ films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS₂ coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS₂ coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS₂ coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS₂ films and improve their tribological performance. Full article

Wood modification with graphene oxide can give it unique features characteristic of other materials. However, the durability of the newly acquired features is of great importance. To better understand them, it is worth conducting an in-depth analysis of the structural changes that occur in wood under the influence of modification with graphene oxide. As part of the research, wood was impregnated with aqueous graphene oxide dispersion. Wood was impregnated using two methods: single vacuum and pressureless with ultrasound. Laser-assisted ionization spectroscopy (LIBS) was used to determine elements, mainly carbon, and to characterize differences in the elemental composition between the surface layers of wood impregnated with graphene oxide and native wood. Changes in the structure of polymers building wood tissue were analyzed using LIBS and FTIR spectrometry. The wood surface was also imaged using three microscopic techniques (stereomicroscope, confocal laser scanning microscope, and scanning electron microscopy). LIBS showed that graphene oxide was deposited on the surface of impregnated wood, and the intensity of carbon signals in wood impregnated with graphene oxide using vacuum and ultrasound differed. The content of carbon, magnesium, and oxygen elements in the surface layers of wood impregnated with graphene oxide using ultrasound was lower than in vacuum-impregnated wood. Analysis of FTIR spectra showed effective incorporation of graphene oxide into the surface layer of wood. Full article