Search Results (120)

The precursor-derived ceramic route is recognized as an advanced and efficient technique for fabricating ceramic matrix composites, particularly suitable for the development and microstructural tailoring of continuous fiber-reinforced ceramic matrix composites. In this work, octamethylcyclotetrasiloxane and tetravinylcyclotetrasiloxane were employed as monomers to synthesize a branched siloxane via ring-opening polymerization. A subsequent hydrosilylation reaction led to the formation of polyvinylsiloxane with a three-dimensional crosslinked structure. The precursor exhibited excellent fluidity, adjustable viscosity, and superior thermosetting characteristics, enabling efficient impregnation and densification of reinforcements through the polymer infiltration and pyrolysis process. Upon pyrolysis, the polyvinylsiloxane gradually converted from an organic polymer to an amorphous inorganic ceramic phase, yielding silicon oxycarbide ceramics with a high ceramic yield of 81.3%. Elemental analysis indicated that the resulting ceramic mainly comprised silicon and oxygen, with a low carbon content. Furthermore, the material demonstrated a stable dielectric constant (~2.5) and low dielectric loss (<0.01), which are beneficial for enhanced thermal stability and dielectric performance. These findings offer a promising precursor system and process reference for the low-cost production of high-performance, multifunctional ceramic matrix composites with strong potential for engineering applications. Full article

In most commercial lithium-ion batteries, graphite remains the primary anode material. However, its theoretical specific capacity is only 372 mAh∙g⁻¹, which falls short of meeting the demands of high-performance electronic devices. Silicon anodes, despite boasting an ultra-high theoretical specific capacity of 4200 mAh∙g⁻¹, suffer from significant volume expansion (>300%) during cycling, leading to severe capacity fade and limiting their commercial viability. Currently, silicon-based polymer-derived ceramics have emerged as a highly promising next-generation anode material for lithium-ion batteries, thanks to their unique nano-cluster structure, tunable composition, and low volume expansion characteristics. The maximum capacity of the ceramics can exceed 1000 mAh∙g⁻¹, and their unique synthesis routes enable customization to align with diverse electrochemical application requirements. In this paper, we present the progress of silicon oxycarbide (SiOC), silicon carbonitride (SiCN), silicon boron carbonitride (SiBCN) and silicon oxycarbonitride (SiOCN) in the field of LIBs, including their synthesis, structural characteristics and electrochemical properties, etc. The mechanisms of lithium-ion storage in the Si-based anode materials are summarized as well, including the key role of free carbon in these materials. Full article

Graphene oxide (GO), a derivative of graphene, has attracted significant attention in tribological applications due to its unique structural, mechanical, and chemical properties. This review highlights the influence of GO and its composites on friction and wear performance across various engineering systems. The paper explores GO’s key properties, such as its high surface area, layered morphology, and abundant functional groups. These features contribute to reduced shear resistance, tribofilm formation, and improved load-bearing capacity. A detailed analysis of GO-based composites, including polymer, metal, and ceramic matrices, reveals those small additions of GO (typically 0.1–2 wt%) result in substantial reductions in coefficient of friction and wear rate, with improvements ranging between 30–70%, depending on the application. The tribological mechanisms, including self-lubrication, dispersion, thermal stability, and interface interactions, are discussed to provide insights into performance enhancement. Furthermore, the effects of electrochemical environment, functional group modifications, and external loading conditions on GO’s tribological behavior are examined. Despite these advantages, challenges such as scalability, agglomeration, and material compatibility persist. Overall, the paper demonstrates that GO is a promising additive for advanced tribological systems, while also identifying key limitations and future research directions. Full article

Cultural Heritage is a vital socioeconomic driver that must contend with works of art continuously exposed to degradation processes, which are further exacerbated by climate change. Aged coatings, varnishes, and soil can compromise the appearance of artworks, preventing their preservation and valorization. In response, soft matter and colloidal systems, such as nanostructured cleaning fluids (NCFs), have proved to be valuable solutions for safely and effectively cleaning works of art. Here, a novel cleaning system is proposed, for the first time employing microgels of poly(N-isopropylacrylamide) (PNIPAM) with surface chains of oligoethylene glycol methyl ether methacrylate (OEGMA) to favor shear deformation by lubrication. These microgels are loaded with NCFs featuring “green” solvents and different kinds of bio-derived or petroleum-based surfactants (non-ionic, zwitterionic). Rheological characterization of the combined systems highlighted a sharp transition from solid to liquid-like state in the 21–24 °C range when the zwitterionic surfactant dodecyldimethylamine oxide was used; the system displays a solid-like behavior at rest but flows easily at intermediate strains. At slightly higher temperature (>24 °C), an inversion of the G′, G″ values was observed, leading to a system that behaves as a liquid. Such control of rheological behavior is significant for feasible and complete removal of soiled polymer coatings from textured ceramic surfaces, which are difficult to clean with conventional gels, without leaving residues. These results position the PNIPAM-OEGMA microgels as promising cleaning materials for the conservation of Cultural Heritage, with possible applications also in fields where gelled systems are of interest (pharmaceutics, cosmetics, detergency, etc.). Full article

Boron-modified ceramic materials derived from polymers (PDC) are the subject of this research. The primary objective is to compare the structure and microstructure of SiBOC materials obtained in varying pyrolysis conditions in comparison to base SiOC materials. The preparation involved a number of stages, staring with the hydrolytic polycondensation method, followed by the initial thermal treatment and the final stage—pyrolysis process in argon or argon/hydrogen atmospheres at different temperatures. Bulk SiOC and SiBOC glasses were thoroughly analyzed. Microstructure studies included Scanning Electron Microscopy and Mercury Intrusion Porosimetry. Moreover, to confirm the structure, the research consisted of Fourier-Transform Infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. The conducted research confirmed boron incorporation into the material structure in all samples. A free carbon phase has also been observed in SiBOC glasses, which has been confirmed in Raman spectroscopy measurements. This research indicates that in particular conditions, it is possible to obtain amorphous materials with nanocrystalline inclusions. This paper proves that the introduction of boron increases the porosity of materials and enhances their thermal stability. Full article

Precursor-derived silicon carbide (SiC) ceramics have been widely used as absorbing materials, but the residual carbon sink produced by ceramicization limits their application under high-temperature and oxygen-containing conditions, such as the nozzle or jet vane of high-speed aircraft. In this paper, a novel molybdenum carbide/silicon carbide (Mo₂C/SiC) microwave-absorbing ceramic with a two-dimensional sheet structure was obtained through the pyrolysis of polycarbosilane-coated molybdenum sulfide (PCS@MoS₂). The results indicate that addition of an appropriate amount of MoS₂ can react with the free carbon generated during the pyrolysis of PCS, thereby reducing the material’s carbon content and forming Mo₂C. Concurrently, the layered structural characteristics of MoS₂ are utilized to create a two-dimensional composite structure within the material, which enhances the material’s absorption vastly. The as-prepared Mo₂C/SiC ceramics sintered at 1300 °C exhibit a minimum reflection loss (RL_min) of −46.49 dB at 8.96 GHz with a thickness of 2.6 mm. Additionally, the effective absorption bandwidth (EAB) of Mo₂C/SiC spans the entire X-band (8–12 GHz) due to the combined effect of multiple loss mechanisms. Full article

Si₃N₄ ceramics and composites stand out for their exceptional mechanical and thermal properties. Compared with conventional ceramic forming processes, 3D printing via vat photopolymerization not only ensures high geometric precision but also improves the forming efficiency and strength of green body. Nevertheless, the grayish appearance of Si₃N₄ and its relatively high refractive index can adversely affect the photocuring behavior in ceramic slurries. The primary objectives focus on enhancing the curing performance and rheological properties of slurries, minimizing defects during post-processing, and improving the relative density and mechanical properties of Si₃N₄ ceramics. Key advancements include slurry optimization via refractive index matching, biomodal particle gradation and surface modification, while the integration of whisker/fiber additions or polymer-derived ceramic strategies enhances mechanical properties. In addition, controlling the atmosphere and heating rate of the post-processing innovations can achieve a relative density of more than 95%. This paper introduces the mechanisms of vat photopolymerization and then summarizes the strategies for improving Si₃N₄ ceramic slurries as well as controlling the printing and debinding/sintering processes. It further highlights the ways in which different approaches can be used to enhance the properties of Si₃N₄ slurries and ceramic parts. Finally, applications of Si₃N₄ ceramics and composites via vat photopolymerization in various fields such as aviation, aerospace, energy, electronics, chemical processes, and biomedical implants are also presented to point out future opportunities and challenges. Full article

Our research outlines a method for creating chemosensors utilizing hybrid nanostructures derived from TiO₂ ceramic nanotubes alongside conducting polymers, with embedded gold nanoparticles. The method used to create hybrid nanostructures from ceramic nanotubes and conducting polymers was drop-casting. AFM analysis highlighted an increased roughness, particularly for PANI-EB, exhibiting a significantly larger grain size exceeding 3.5 μm, with an increased inclusion of gold and uniform arrangement on the surface. The Rku parameter values being around three suggested that the layers primarily exhibited peaks rather than depressions, showing a Gaussian distribution. A chemiresistor was created by using an ink-jet printer and a multilayer metallization was achieved with commercial silver ink for printed electronics. Based on the experimental calibration curve, which exhibits adequate linearity over a wider range of H₂S concentrations in air up to 1 ppm, the detection limit was established at 0.1 ppm, a threshold appropriate for recognizing oral diseases. The sensor is a simple, affordable, and durable device designed for individual use, offering significant benefits for patients by enabling improved tracking of the syndrome’s advancement or treatment success. Full article

Polymer-derived SiOC ceramics (PDC_s-SiOC) possess advantages such as high temperature resistance, oxidation resistance, corrosion resistance, and customizable mechanical and dielectric properties. These attributes make them a promising material for high-temperature structural and functional applications. Based on polymer-derived ceramic conversion technology, this study synthesized a photosensitive resin with high ceramic yield and low shrinkage from commercial MK resin, 3-(trimethoxysilyl) propyl methacrylate, and trimethylolpropane triacrylate monomer. Using digital light processing additive manufacturing technology, 3D diamond-structured SiOC ceramic and 3D octahedron-structured SiOC ceramic with high precision were fabricated. The pyrolysis of both structures at different temperatures (1000 °C to 1400 °C) yielded SiOC ceramics, which exhibited uniform shrinkage in all directions, with a linear shrinkage rate ranging from 31% to 36%. The microstructure was characterized by FTIR, XRD, and SEM, respectively. Additionally, the compressive strength and elastic modulus of the three-dimensional SiOC ceramics were studied. The SiOC ceramic diamond lattice structure, fabricated through pyrolysis at 1200 °C, demonstrated good mechanical properties with a geometric density of 0.76 g/cm³. Its compressive strength and elastic modulus were measured at 7.66 MPa and 1.47 GPa, respectively. This study offers valuable insights into the rapid and customized manufacturing of lightweight ceramic structures. Full article

Titanium possesses many useful properties and is a technologically important material in engineering. However, lubrication of titanium has long been a problem that has prevented titanium from being more widely used. This is due to its poor tribological properties, deriving from its high tendency towards adhesive wear, material transfer, and abrasive wear. Lubrication is a system engineering which involves material combinations, material surfaces, lubricants, and operating conditions as a system. In this work, the boundary lubrication behavior of commercially pure titanium (CP-Ti) sliding against various counterbody materials in a motor oil (0W-30) was investigated under ball-on-plate reciprocating sliding conditions. The counterbody materials (balls) include CP-Ti, ceramic (Al₂O₃), steel (AISI 52100), and polymer (nylon). The results show that depending on material combination, the lubricating behavior can be divided into three categories, i.e., (1) lubrication failure (Ti-Ti), (2) improved lubrication but with friction instability (Ti-Al₂O₃), and (3) effective lubrication (Ti–steel and Ti–nylon). Lubrication failure of the Ti-Ti pair leads to high and unstable friction and severe wear from both the plate and ball, while friction instability of the Ti-Al₂O₃ pair leads to friction spikes and high wear rates. Effective lubrication of the Ti–steel pair results in low and smooth friction and much-reduced wear rates of the Ti plate by nearly 10,000 times. However, there is a load-dependence of the lubrication effectiveness of the Ti–steel pair. Although the Ti–nylon pair is effectively lubricated in terms of much-reduced friction, the nylon ball suffers from severe wear. The friction and wear mechanisms of the various sliding pairs are discussed in this paper. Full article

The growing need for sustainable materials in engineering applications has led to increased interest in the use of waste-derived ceramics as reinforcing fillers in polymer composites. This study investigates the mechanical and tribological performance of epoxy composites reinforced with Yttria-Stabilized Zirconia (YSZ) waste ceramics, focusing on the effects of varying ceramic content (0–40 wt.%). The results demonstrate that while the tensile strength decreases with increasing ceramic content, the wear resistance and surface hardness improve, particularly at 20 wt.% YSZ. These findings are highly relevant for industries such as automotive, aerospace, and industrial manufacturing, where the demand for eco-friendly, high-performance materials is growing. This work aligns with the journal’s focus on sustainable engineering by offering new insights into the practical application of waste materials in high-performance composite systems. Full article

The development of new encapsulating coatings for flexible solar cells (SCs) can help address the complex problem of the short lifespan of these devices, as well as optimize the technological process of their production. In this study, new laminate-type protective composite coatings were prepared using a silicon oxynitride thin-film matrix obtained by curing the pre-ceramic polymer perhydropolysilazane (PHPS) through two low-temperature methods: (i) thermal annealing at 180 °C and (ii) exposure to UV radiation at wavelengths of 185 and 254 nm. Single-walled carbon nanotubes (SWCNTs) were used as fillers via dry transfer, facilitating their horizontal orientation within the matrix. The optical, adhesive, and structural properties of the matrix films and SiO_xN_y/SWCNT composite coatings, along with their long-term stability, were studied using Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, HR-SEM, spectral ellipsometry, and a progressive-load scratch test. In this work, the optical constants of PHPS-derived films were systematically studied for the first time. An antireflection effect was observed in the composites revealing their two-component nature associated with (i) the refractive index of the SiO_xN_y matrix film and (ii) the embedding of a SWCNT filler into the SiO_xN_y matrix. The curing method of PHPS was shown to significantly affect the resulting properties of the films. In addition to being used as protective multifunctional coatings for SCs, both SiO_xN_y/SWCNT composites and SiO_xN_y matrix films also function as broadband optical antireflective coatings. Furthermore, due to the very low friction coefficients observed in the mechanical tests, they show potential as scratch resistant coatings for mechanical applications. Full article

The emerging paradigm of personalised bone repair embodies a transformative triad comprising bio-inspired design, digital fabrication, and the exploration of innovative materials. The increasing average age of the population, alongside the rising incidence of fractures associated with age-related conditions such as osteoporosis, necessitates the development of customised, efficient, and minimally invasive treatment modalities as alternatives to conventional methods (e.g., autografts, allografts, Ilizarov distraction, and bone fixators) typically employed to promote bone regeneration. A promising innovative technique involves the use of cellularised scaffolds incorporating mesenchymal stem cells (MSCs). The selection of materials—ranging from metals and ceramics to synthetic or natural bio-derived polymers—combined with a design inspired by natural sources (including bone, corals, algae, shells, silk, and plants) facilitates the replication of geometries, architectures, porosities, biodegradation capabilities, and mechanical properties conducive to physiological bone regeneration. To mimic internal structures and geometries for construct customisation, scaffolds can be designed using Computer-aided Design (CAD) and fabricated via 3D-printing techniques. This approach not only enables precise control over external shapes and internal architectures but also accommodates the use of diverse materials that improve biological performance and provide economic advantages. Finally, advanced numerical models are employed to simulate, analyse, and optimise the complex processes involved in personalised bone regeneration, with computational predictions validated against experimental data and in vivo studies to ascertain the model’s ability to predict the recovery of bone shape and function. Full article

A dense monolithic SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C high-entropy ceramic nanocomposite was prepared using a polymer-derived ceramic (PDC) method combined with spark plasma sintering (SPS). The microstructural evolution and mechanical properties of the obtained nanocomposites were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning-electron microscope (SEM), and nanoindentation. The results indicate that the phase composition of SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C can be adjusted by modifying the metal content of the single-source precursor (SSP) through molecular design. The resulting precursor exhibits an exceptionally high ceramic yield, with mass retention of over 90% at 1100 °C, which guarantees the densification of the final SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C composites. The PDC route facilitates the in situ formation of a high-entropy phase within the ceramic matrix under low temperature pyrolysis conditions. Combined with SPS, a dense monolithic SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C nanocomposite was obtained, exhibiting an open porosity of 0.41 vol%, nano-hardness of 27.47 ± 0.46 GPa, elastic modulus of 324.00 ± 13.60 GPa, and fracture toughness of 3.59 ± 0.24 MPa·m^0.5, demonstrating excellent mechanical properties. Full article

Polymer-derived silicon oxycarbide (SiOC) ceramics have garnered significant attention as novel silicon-based anode materials. However, the low conductivity of SiOC ceramics is a limiting factor, reducing both their rate capability and cycling stability. Therefore, controlling the free carbon content and its degree of graphitization within SiOC is crucial for determining battery performance. In this study, we regulated the free carbon content using divinylbenzene (DVB) and controlled the graphitization of free carbon with the transition metal iron (Fe). Through a simple pyrolysis process, we synthesized SiOC ceramic materials (CF) and investigated the impact of Fe-induced changes in the carbon phase and the amorphous SiOC phase on the comprehensive electrochemical performance. The results demonstrated that increasing the DVB content in the SiOC precursor enhanced the free carbon content, while the addition of Fe promoted the graphitization of free carbon and induced the formation of carbon nanotubes (CNTs). The electrochemical performance results showed that the CF electrode material exhibited a high reversible capacity of approximately 1154.05 mAh g⁻¹ at a low current density of 100 mA g⁻¹ and maintained good rate capability and cycling stability after 1000 cycles at a high current density of 2000 mA g⁻¹. Full article