Search Results (138)

 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

Carbon fiber-reinforced composites (CFRCs) have attracted considerable attention in recent years due to their excellent properties, enabling their use across various sectors. However, their application at high temperatures is limited by the fibers’ lack of oxidation resistance. This study demonstrates a significant advancement in enhancing the oxidation stability performance of carbon fiber-reinforced composites (CFRCs) by developing a silicon carbide (SiC) coating through the ceramization of carbon fibers using silicon (Si) powder. For the first time, this method was applied to recycled carbon fibers from CF thermoplastic composites. The key findings include the successful formation of a uniform SiC coating, with coating thickness increasing with process duration and decreasing at higher temperatures. The treated fibers exhibited substantially improved oxidation resistance, maintaining structural stability above 700 °C—markedly better than that of their uncoated counterparts. Thermogravimetric analysis confirmed that oxidation resistance varied depending on the CF/Si ratio, highlighting this parameter’s critical role. Overall, this study offers a viable pathway to enhance the thermal durability of recycled carbon fibers for high-temperature applications. Full article

Additive manufacturing (AM) is one of the most frequently used technologies to produce complex configuration products. Moreover, AM is very well known as a technology which is characterized by a low amount of generated waste and the potential to be called zero-waste technology. As is known, there are seven main groups of technologies described in the ISO/ASTM 52900 standard that allow the use of very different materials from polymers to metals, ceramics, and composites. However, the increased utilization of additively manufactured composites for different applications requires a deeper analysis of production processes and materials’ characteristics. Various AM technologies can be used to produce complex composite structures reinforced with short fibers; however, only material extrusion (MEX)-based technology is used for the production of composites reinforced with continuous fibers (CFs). At this time, five different methods exist to produce CF-reinforced composite structures. This study focuses on co-extrusion with the towpreg method. Because of the complexity and layer-by-layer nature of the process, defects can occur during production, such as poor interlayer adhesion, increased porosity, insufficient impregnation, and others. To eliminate or minimize defects’ influence on mechanical properties and structural integrity of additively manufactured structures, a hypothesis was proposed involving heat treatment. Carbon fiber’s conductive properties can be used to heal the composite structures, by heating them up through the application of electric current. In this research article, an experimental evaluation of conditions for additively manufactured composites with continuous carbon fiber reinforcement for self-healing processes is presented. Mechanical testing was conducted to check the influence of heat treatment on the flexural properties of the composite samples. Full article

This study aimed to comparatively evaluate the effects of various surface treatment protocols on the shear bond strength (SBS) between heat-polymerized polymethyl methacrylate (PMMA) and different CAD/CAM framework materials, including cobalt–chromium (Co–Cr) alloys, ceramic particle-reinforced polyetheretherketone (PEEK), and glass fiber-reinforced composite resin (FRC). A total of 135 disc-shaped specimens were prepared from Co–Cr, PEEK, and FRC materials. Surface treatments specific to each material, including airborne-particle abrasion, sulfuric acid etching, laser irradiation, plasma activation, and primer application, were applied. PMMA cylinders were polymerized onto the treated surfaces, and all specimens were subjected to 30,000 thermal cycles. SBS values were measured using a universal testing machine, and the failure modes were classified. The normality of data distribution was assessed using the Kolmogorov–Smirnov test, and the homogeneity of variances was evaluated using Levene’s test. Group comparisons were performed using the Kruskal–Wallis test, and Dunn’s post hoc test with Bonferroni correction was applied in cases where significant differences were detected (α = 0.05). The highest SBS values (~27–28 MPa) were obtained in the Co–Cr group and in the PEEK groups treated with sulfuric acid and primer. In contrast, the PEEK group with additional laser treatment exhibited a lower SBS value. The untreated PEEK group showed significantly lower SBS (~3.9 MPa) compared to all other groups. The Trinia groups demonstrated intermediate SBS values (16.5–17.4 MPa), which exceeded the clinically acceptable threshold of 10 MPa. SEM observations revealed material- and protocol-specific surface responses; plasma-treated specimens maintained topographic integrity, whereas laser-induced surfaces showed localized degradation, particularly following dual-step protocols. Fracture mode analysis indicated that higher SBS values were associated with cohesive or mixed failures. SEM observations suggested that plasma treatment preserved surface morphology more effectively than laser treatment. This study highlights the importance of selecting material-specific surface treatments to optimize bonding between CAD/CAM frameworks and PMMA. Sulfuric acid and primer provided strong adhesion for PEEK, while the addition of laser or plasma offered no further benefit, making such steps potentially unnecessary. Trinia frameworks also showed acceptable performance with conventional treatments. These findings reinforce that simplified conditioning protocols may be clinically sufficient, and indicate that FRC materials like Trinia should be more fully considered for their broader clinical potential in modern CAD/CAM-based prosthetic planning. Full article

Thermal protection materials with excellent performance are critical for hypersonic vehicles. Carbon fiber/phenolic resin composites (C_f/Ph) have been widely used as thermal protection materials due to their high specific strength and ease of processing. However, oxidative failure limits the extensive applications of C_f/Ph in harsh environments. In this paper, a novel hafnium carbide (HfC) and boron carbide (B₄C)-modified C_f/Ph was fabricated via an impregnating and compression molding route. The synergistic effect of HfC and B₄C on the thermal stability, flexural strength, microstructure, and phase evolution of the ceramizable composite was studied. The resulting ceramizable composites exhibited excellent resistance to oxidative corrosion and ablation behavior. The residual yield at 1400 °C and the flexural strength after heat treatment at 1600 °C for 20 min were 46% and 54.65 MPa, respectively, with an increase of 79.59% in flexural strength compared to that of the composites without ceramizable fillers. The linear ablation rate (LAR) and mass ablation rate (MAR) under a heat flux density of 4.2 MW/m² for the 20 s were as low as −8.33 × 10⁻³ mm/s and 3.08 × 10⁻² g/s. The ablation mechanism was further revealed. A dense B–C–N–O–Hf ceramic layer was constructed in situ as an efficient thermal protection barrier, significantly reducing the corrosion of the carbon fibers. Full article

Lightweight, high-temperature thermal insulation materials play a critical role in aerospace applications, where extreme temperature conditions necessitate lightweight, high-performance solutions. This paper explores advancements in lightweight, high-temperature insulation materials specifically designed for aerospace environments, focusing on innovative flexible ceramic fiber felts, thermal insulation tiles, nano-insulation materials (aerogels), and multilayer insulations (MLIs). These materials exhibit superior thermal resistance, low density, and durability under dynamic and harsh conditions. Key developments include the integration of nanostructures to enhance thermal conductivity control and improve mechanical stability. This paper also highlights applications in spacecraft thermal protection systems, providing insights into the challenges of future material design strategies. These advancements underscore the growing potential of thermal insulations to improve energy efficiency, safety, and performance in aerospace missions. Full article

This study investigates the application of spinel (MgAl₂O₄) hollow fiber membranes for clarification of clove basil (Ocimum gratissimum L.) aqueous extract, a rich source of bioactive compounds. The membranes were produced using a phase-inversion and sintering method at 1350 °C, combining alumina and dolomite as raw materials. The calcination of the powder materials at 1350 °C resulted in the spinel phase formation, as indicated by the XRD analyses. The spinel hollow fiber membrane presented a hydrophilic surface (water contact angle of 74°), moderate roughness (144.31 ± 12.93 nm), and suitable mechanical strength. The ceramic membrane demonstrated a water permeability of 35.28 ± 2.46 L h⁻¹ m⁻² bar⁻¹ and a final permeate flux of 9.22 ± 1.64 L h⁻¹ m⁻² for filtration of clove basil extract at 1.0 bar. Fouling analysis identified cake formation as the dominant mechanism for flux decline. The membrane retained 44% of the total phenolic compounds and reduced turbidity by 60%, while preserving significant antioxidant capacity in the permeate. The results highlight the potential of spinel-based hollow fiber membranes as a cost-effective and efficient solution for clarifying bioactive plant extracts, offering enhanced mechanical properties and lower sintering temperatures compared to conventional alumina membranes. Full article

In recent years, there has been increasing interest in new materials such as ceramic matrix composites (CMCs) for power generation and aerospace propulsion applications through hydrogen combustion. This study employed a deep artificial neural network (DANN) model to predict the ablation performance of CMCs in the hydrogen torch test (HTT). The study was conducted in three phases to increase the accuracy of the model’s predictions. Initially, to predict the thermal behavior of ceramic composites, two linear machine learning models were used known as Lasso and Ridge regression. In the second step, four decision tree-based ensemble machine learning models, namely random forest, gradient boosting regression, extreme gradient boosting regression, and extra tree regression, were used to improve the prediction accuracy metrics, including root mean square error (RMSE), mean absolute error (MAE), correlation coefficient (R² score), and mean absolute percentage error (MAPE), relative to the previously introduced linear models. Finally, to forecast the thermal stability of CMCs with time, an optimized DANN model with two hidden layers having rectified linear unit activation function was developed. The data collection procedure involved preparing CMCs with continuous Yttria-Stabilized Zirconia (YSZ) fibers and silicon carbide (SiC) matrix using a polymer infiltration and pyrolysis (PIP) technique. The samples were exposed to a hydrogen flame at a high heat flux of 183 W/cm² for a duration of 10 min. A good agreement between the DANN model’s predictions and experimental data with an R² score of 0.9671, RMSE of 16.45, an MAE of 14.07, and an MAPE of 3.92% confirmed the acceptability of the developed neural network model in this study. Full article

Random lasers (RLs) based on glasses and glass-ceramics doped with rare-earth ions (REI) deserve great attention because of their specific physical properties such as large thermal stability, possibility to operate at high intensities, optical wavelength tunability, and prospects to operate Fiber-RLs, among other characteristics of interest for photonic applications. In this article, we present a brief review of experiments with RLs based on tellurite and germanate glasses and glass-ceramics doped with neodymium (Nd³⁺), erbium (Er³⁺), and ytterbium (Yb³⁺) ions. The glass samples were fabricated using the melt-quenching technique followed by controlled crystallization to achieve the glass-ceramics. Afterwards, the samples were crushed to obtain the powder samples for the RLs experiments. The experiments demonstrated RLs emissions at various wavelengths, with feedback mechanisms due to light scattering at grain/air and crystalline/glass interfaces. The phenomenon of replica symmetry breaking was verified through statistical analysis of the RLs intensity fluctuations, indicating a photonic phase-transition (corresponding to the RL threshold) analogous to the paramagnetic-to-spin glass transition in magnetic materials. The various results reported here highlight the potential of glasses and glass-ceramics for the development of RLs with improved performance in terms of reduction of laser threshold and large lifetime of the active media in comparison with organic materials. Full article

Traditional nanoparticle aerogels suffer from inherent brittleness and thermal instability at elevated temperatures. In recent years, ceramic nanofiber aerogels, utilizing flexible nanofibers as structural units, have emerged as mechanically resilient alternatives with ultrahigh porosity (>90%). However, their thermal insulation capabilities are compromised by micron-scale pores (10–100 μm) and overdependence on ultralow density, which exacerbates mechanical fragility. This study pioneers a gas-phase self-assembly strategy to fabricate Si₃N₄ nanoparticle reinforced Si₃N₄ nanofiber aerogels (SNP-R-SNFA) with gradient pore architectures. By leveraging methyltrimethoxysilane/vinyltriethoxysilane composite aerogel (MVa) as a reactive template, we achieved spontaneous growth of Si₃N₄ nanofiber films (SNP-R-SNF) featuring nanoparticle-fiber interpenetration and porosity gradients. The microstructure formation mechanism of SNP-R-SNF was analyzed using field-emission scanning electron microscopy. Layer assembly and hot-pressing composite technology were employed to prepare the SNP-R-SNFA, which showed low density (0.033 g/cm³), exceptional compression resilience, insensitive frequency dependence of dielectric properties (ε′ = 2.31–2.39, tan δ < 0.08 across 8–18 GHz). Infrared imaging displayed backside 893 °C cooler than front, demonstrating superior insulation performance. This study not only provides material solutions for integrated electromagnetic wave-transparent/thermal insulation applications but more importantly establishes an innovative paradigm for enhancing the mechanical robustness of nanofiber-based aerogels. Full article

Aiming at the issues of low sensitivity and poor resistance to temperature and vibration interference in traditional optical fiber current transformers, as well as the structural complexity of magnetostrictive material-coupled sensors, this paper integrates a high-sensitivity electrostrictive piezoelectric ceramic sensor with an FBG-FP cascaded fiber-optic sensor. This coupling significantly optimizes the sensor structure. By employing orthogonal intensity demodulation to enhance detection sensitivity, and adopting a multi-cycle waveform-averaging method to calculate the DC output light intensity, temperature calibration and compensation are achieved through the correlation between the DC output light intensity and operating points. Experimental results demonstrate that the designed sensor exhibits a detection bandwidth of 0–7 kHz, fully meeting the requirements for power-frequency current detection. Its current measurement range spans 0.15–42 mA, with a minimum measurable current as low as 150 μA. This study provides a compact, high-precision, highly scalable, and adaptable current detection solution for power systems, demonstrating significant engineering application value. Full article

There has been growing interest and increasing attention in the field of functional clothing textiles, particularly in product and process development, as well as innovations in heat-generating, retaining, and releasing fibers to maintain a healthy body temperature without relying on unsustainable energy sources. This study, for the first time, reports the various physio-mechanical properties of surface-functionalized regenerated cellulose fibers (RCFs) coated with ceramic particles. The coating imparts photothermal conversion-based heat generation and retention properties with the aid of polyelectrolyte binders. In this design, ZrC enables the conversion of light energy into thermal energy, providing heat for the human body. A feasible coating process was employed, utilizing industrially feasible exhaustion methods to deposit the ZrC particles onto the RCF surface in conjunction with two distinctive polymeric binders, specifically polyethyleneimine (PEI) and polydiallyldimethylammonium chloride (polyDADMAC). The morphological characteristics and tensile properties of the coated RCFs were analyzed via scanning electron microscopy (SEM) and single-fiber tensile testing. Heat retention and release behaviors of a bundle of fiber samples were assessed using infrared (IR) imaging and an IR emission lamp setup. The SEM results confirmed the successful coating of the ZrC particles on the surface of the RCF samples, influencing negligible on their physical–mechanical properties. The heat retention of the coated RCFs with ZrC and both binders was higher than that of reference regenerated cellulose fibers (RCFs), demonstrating their effective heat generation, retention, and heat release properties. Based on the highlighted prominent results for the coated RCFs, these findings highlight the suitability of the developed functional clothing textiles for targeted applications in non-extreme thermal conditions, ensuring thermo-physiological comfort by maintaining body temperature within a tolerable thermal range (36.5–37.5 °C), in contrast to studies reporting significantly higher temperatures (50–78 °C) for extreme thermal conditions. 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

The growing demand for sustainable energy solutions requires the development of safe and efficient systems for hydrogen utilization. Hydrogen, with its high energy density and clean combustion characteristics, has become a promising alternative for heating applications. However, conventional combustion technologies often suffer from inefficiencies and safety concerns, such as NO_x emissions and explosion risks. To address these challenges, this study aimed to design and evaluate a catalytic heat generator utilizing hydrogen–air mixtures under controlled conditions to eliminate the need for pure oxygen and mitigate associated risks. A single-bed catalytic system was developed using palladium-based catalysts supported on ceramic fibers, followed by its heating, activation, and further characterization using the SEM-EDS technique. A multi-bed generator was later constructed to enhance scalability and performance. Thermal imaging and temperature monitoring were employed to optimize activation processes and assess system performance under varying hydrogen flow rates. The experimental results demonstrated efficient heat transfer and operational stability. Full article

The piezoelectric grating voltage sensor has garnered significant attention in the realm of intelligent sensing, attributed to its compact size, cost-effectiveness, robust electromagnetic interference (EMI) immunity, and high network integration capabilities. In this paper, we propose a PZT-FBG (piezoelectric ceramic–fiber Bragg grating) voltage–temperature demodulation optical path architecture. This scheme effectively utilizes the originally unused temperature compensation reference grating, repurposing it as a temperature measurement grating. By employing FBGs with identical or similar parameters, we experimentally validate two distinct optical path connection schemes, before and after optimization. The experimental results reveal that, when the input voltage ranges from 250 V to 1800 V at a frequency of 50 Hz, the goodness of fit for the three fundamental waveforms is 0.996, 0.999, and 0.992, respectively. Furthermore, the sensor’s frequency response was tested across a frequency range of 50 Hz to 20 kHz, demonstrating that the measurement system can effectively respond within the sensor’s operational frequency range. Additionally, temperature measurement experiments showed a goodness of fit of 0.997 for the central wavelength of the FBG as the temperature increased. This research indicates that the improved optical path connection method not only accomplishes a synchronous demodulation of both temperature and voltage parameters but also markedly enhances the linearity and resolution of the voltage sensor. This discovery offers novel insights for further refining sensor performance and broadening the applications of optical voltage sensors. Full article