This is the closing issue of 2024. It offers a review on electromagnetic shielding coating for aerospace applications,1 and seven original research reports on novel hybrid nanocomposite for optical devices,2 fabrication of a highly flexible gallium-indium electrode for soft electronics,3 nanocomposite films for electric heating,4 nickel-copper (Ni-Cu) alloy coating on neodymium (NdFeB) magnets,5 nickel-phosphorous (Ni-P) coating for solar adsorption technology,6 ordered titanium dioxide (TiO2) nanotubes formed on Ti-based alloys,7 and nano-textured hydrophobic coating fabricated by galvanic corrosion.8
Featured Article1 explores the characterization, thermal behavior, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) of thin coatings made of zirconium diboride (ZrB2) and its composites. It analyzes surface morphology, microstructural properties, and grain sizes before and after annealing, highlighting structural changes and thermal stability. It also examines the films' responses to temperature variations, focusing on stability, mechanical integrity, and performance under extreme conditions. XRD reveals crystalline structure transformations and grain size variations, while XPS enhances understanding of chemical composition, bonding structures, and surface oxidation. This comprehensive study advances knowledge of materials for stealth technology and influences future scientific research and applications, particularly in the aerospace and defense sectors.
The first original contribution to this issue describes the formulation of novel polymer nanocomposites specifically intended to be attractive in optoelectronic devices, including solar cell applications.2 Using oxidative polymerization and solution casting, Abdeltwab et al. formulated poly-4-chloroaniline film filled with 30–40 nm iron oxide (Fe2O3) particles. The nanocomposite formulated exhibited uniform structure and good bonding between polymer and iron oxide particles. The researchers found that as the Fe2O3 content increased from 3 to 9 wt%, the dispersion energy values increased and the relaxation time for poly-4-chloroaniline decreased. The presence of nanoparticles also affected the permittivity and optical conductivity of the polymer, leading to improvements in both linear and non-linear optical characteristics of the nanocomposite. Readers are encouraged to review the previous nanocomposites papers9–10 published by this team in the Surface Innovations journal.
In the next article of this issue, researchers from the Korea Institute of Industrial Technology present groundbreaking work on creating flexible liquid metal electrodes.3 They combined a highly flexible gallium-indium (Ga-In) liquid metal electrode with a UV-curable polyurethane acrylate polymer. The authors demonstrate that they could easily pattern the Ga-In liquid metal electrodes using a negative direct patterning technique, which involves using a UV pulsed laser to create patterned, irradiated areas without needing complex photolithography masks. The laser-patterned Ga-In/polyurethane acrylate composite electrode showed exceptional electrical conductivity of 6.3 × 105 S/m, as well as outstanding flexibility and durability. It exhibited minimal resistance decrease under severe cyclic folding fatigue testing. We hope their work will inspire new ideas for wearable and flexible electronic devices, and we would like to invite further contributions to this journal that result from this inspiration.
In the fourth contribution to this issue, researchers from China reveal the fabrication and characterization of multi-layer flexible films.4 The flexible films are made of polyurethane, polydopamine, polypyrrole, and silver and were fabricated through a combination of magnetron sputtering with three-step film scraping, surface grafting, and in situ polymerization. These novel flexible films have the advantages of relatively simple preparation, good environmental stability, adjustable conductivity, and non-toxicity, and they offer a wide range of applications in the field of electric heating.
The NdFeB magnets are commonly used in rail transit systems and must be protected from the surrounding environment's corrosive humidity and reactive constituents. In a new contribution, Long et al.5 describe the deposition of Ni-Cu alloy coating on NdFeB magnets by pulse-reverse current electrodeposition to improve the corrosion resistance of magnets. The authors conducted comprehensive characterizations to investigate the corrosion properties and mechanism of pure Ni and Ni-Cu alloy coatings in 3.5 wt% NaCl solution, including the effect of microstructure on corrosion resistance. The researchers found a high self-healing ability and high corrosion resistance of the Ni-Cu alloy coating. This invention can potentially improve the service lifetime of magnets and widen their application. We also would like the readers to consider reading the previous contribution on this topic published in 2023.11
In the sixth contribution to this issue, an inter-institutional research team from Mexico discusses the manufacturing of a black double-layer Ni-P solar-absorbing film through electroless deposition.6 They utilized an acid nickel sulfate bath as the source of Ni ions and sodium hypophosphite as the reducing agent, which provided P under controlled conditions, including pH, temperature, and concentration of the reducing agent. The films were designed to enhance solar absorption across the solar spectrum, specifically for wavelengths ranging from 250 nm to approximately 2500 nm. For instance, a six-micron thick Ni-P double layer achieved 96% absorption within the 300–2000 nm range. This innovation could generate interest among researchers working on solar power systems.
Titanium oxides are among the most extensively studied materials in science due to their exceptional properties. They find applications in areas such as photocatalysis, dye-sensitized solar cells, and biomedical devices. In a new study, a research team from Turkey reports on the fabrication of well-ordered TiO2 nanotubes on a medical-grade Ti15Mo alloy.7 The team characterized the nanotube structures using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray mapping before and after heat treatment. The study systematically examined the wettability and antibacterial properties of the TiO2 nanotubes produced on the Ti15Mo alloy, confirming their promising antibacterial characteristics and biocompatibility. This innovation is likely to interest researchers focused on implants for dental and orthopedic applications, where implant-related infections are a significant concern. For further insights, readers are directed to a review published in the previous issue, which discusses the manipulation of antimicrobial properties of surfaces through surface nano- and micro-texturing.12
This issue concludes with a paper on the texturing of steel surfaces using the galvanic corrosion technique.8 The researchers from Sun Yat-sen University in China demonstrate the fabrication of superhydrophobic micro/nanostructures with honeycomb-like protrusions and network-like nano-textures, which are converted to hydrophobic and superhydrophobic by applying the perfluorooctanoic acid coating. When immersed in a corrosion solution, the protecting coating shows satisfactory stability and resistance to further corrosion. This treatment is potentially of interest in protecting steel surfaces that have already undergone some corrosion process, particularly in marine engineering equipment.
Finally, please remember that we welcome your feedback and suggestions to enhance the Surface Innovations journal for our readers in the future. We also invite comprehensive reviews and original work related to surface and coating science, engineering, manufacturing, and performance.
