Fiber Felt Research Articles

Bioelectricity production and bioremediation potential of Withania somnifera in plant microbial fuel cells

In p-MFCs living plants photosynthesize within a bio-electrochemical circuit. The plant exudes organic waste material from the roots. In the rhizosphere, bacteria consume these wastes by oxidizing them in contrast to the atmosphere that reduces it. This redox reaction along with photosynthesis can be harnessed as bioelectricity. In this work, the plant Withania somnifera (L.) Dunal was used for generating bioelectricity from the root exudates and organic matter available in the soil. An open circuit voltage of 930±21 mV was achieved between multiple cycles of operation. The cell voltage further increased to 1260±140 mV with enrichment in the form of discards from vegetable matter. The peak recorded voltage was 1400 mV. Graphite fibre felt electrodes ensured uniform microbial growth with power densities that were achieved at 57 mW/m2 and 84 mW/m2 with and without enrichment respectively. ATR-FTIR demonstrated complete degradation of specific compounds attached to the carbon matrix in the soil along with the polysaccharide content from the enrichments. Additionally, this work also monitored the changes in soil pH and its homogeneity, the impact of photosynthetically active radiation, humidity, and the presence of CO2 in the air, and how it affects plant growth and ultimately the microbes at the rhizosphere which accounted for the bioremediation and the resultant bioelectricity production. SEM imaging provided additional evidence that the presence of electrochemically active soil bacteria, an anaerobic environment, and electrode characteristics are crucial for the development of conductive biofilms.

Atomic Confinement Empowered CoZn Dual-Single-Atom Nanotubes for H2O2 Production in Sequential Dual-Cathode Electro-Fenton Process.

Single-atom catalysts (SACs) are flourishing in various fields because of their 100% atomic utilization. However, their uncontrollable selectivity, poor stability and vulnerable inactivation remain critical challenges. According to theoretical predictions and experiments, a heteronuclear CoZn dual-single-atom confined in N/O-doped hollow carbon nanotube reactors (CoZnSA@CNTs) is synthesized via spatial confinement growth. CoZnSA@CNTs exhibit superior performance for H2O2 electrosynthesis over the entire pH range due to dual-confinement of atomic sites and O2 molecule. CoZnSA@CNTs is favorable for H2O2 production mainly because the synergy of adjacent atomic sites, defect-rich feature and nanotube reactor promoted O2 enrichment and enhanced H2O2 reactivity/selectivity. The H2O2 selectivity reaches ∼100% in a range of 0.2-0.65V versus RHE and the yield achieves 7.50M gcat -1 with CoZnSA@CNTs/carbon fiber felt, exceeding most of the reported SACs in H-type cells. The obtained H2O2 is converted directly to sodium percarbonate and sodium perborate in a safe way for H2O2 storage/transportation. The sequential dual-cathode electron-Fenton process promotes the formation of reactive oxygen species (•OH, 1O2 and •O2 -) by activating the generated H2O2, enabling accelerated degradation of various pollutants and Cr(VI) detoxification in actual wastewater. This work proposes a promising confinement strategy for catalyst design and selectivity regulation of complex reactions.

Yttrium Silicate‐Coated Carbon Fiber Reinforced Phenolic Aerogel‐like Composites with Low Density and Low Ablation

AbstractThe evolution of hypersonic vehicles has raised higher requirements for thermal protection materials, which have become the focus of research on how to meet the lightweight and less ablative. Herein, a yttrium silicate‐coated carbon fiber felts (YS‐CFs) reinforced phenolic aerogel‐like (PR) composites were prepared. The YS‐CFs/PR with the addition of 12 % hexamethylenetetramine exhibited low density (0.540 g/cm3), low thermal conductivity (0.145 W/(m⋅K)), and good thermal stability. Specifically, under an oxyacetylene flame examination with 2.44 MW/m2 heated for 120 s, its mass ablation rates (9.833 mg/s) and line ablation rates (5 μm/s) were decreased by 40.8 % and 32.6 %, respectively, compared to others. The results show that the composites with these combined properties can meet the requirements for thermal protection materials in the field of hypersonic vehicles.

Multifunctional flexible carbon fiber felt@nickel composite films with core–shell heterostructure: Exceptional Joule heating capability, thermal management, and electromagnetic interference shielding

Flexible electrothermal materials with multifunctionality have gained paramount importance in both industrial and everyday settings. Nevertheless, achieving exceptional electrothermal performance at ultra-low actuation voltages remains an imposing challenge. This research addresses this challenge by introducing a novel core–shell heterostructure. The unique design incorporates carbon fiber felt (CFF) as the core and envelops it with nickel (Ni) particles through electroplating. The giant core–shell heterostructure endows CFF@Ni to achieve impressive heating temperatures of up to 146.7 °C at only 1.5 V. A proposed linear model offers precise thermal control by correlating saturation temperature with the square of applied voltages. CFF@Ni exhibits rapid heating rates up to 35.8 °C/s, surpassing previous reports, and also possesses robust bending durability and reliable electrothermal characteristics. The electrothermal mechanism analysis manifests that the synergy of enhanced electrical conductivity and the unique heterostructure enables efficient electricity-to-heat conversion. Versatility is demonstrated in diverse applications, from rapid liquid heating to de-icing and thermal therapy. Notably, CFF@Ni excels in microwave shielding and flame retardancy, marking it as an excellent multifunctional material. This research significantly advances the landscape of electrothermal materials, offering a promising avenue for practical, efficient, and durable electric heating solutions that can be applied across various fields.

In Situ Growth of Amorphous MnO2 on Graphite Felt via Mild Etching Engineering as a Powerful Catalyst for Advanced Vanadium Redox Flow Batteries.

Owing to the advantages of low cost, high safety, and a desirable cycling lifetime, vanadium redox flow batteries (VRFBs) have attracted great attention in the large-scale energy storage field. However, graphite felts (GFs), widely used as electrode materials, usually possess an inferior catalytic activity for the redox reaction of vanadium ions, largely limiting the energy efficiency and rate performance of VRFBs. Here, an in situ growth of amorphous MnO2 on graphite felt (AMO@GF) was designed for application in VRFBs via mild and rapid etching engineering (5 min). After the etching process, the graphite felt fibers showed a porous and defective surface, contributing to abundant active sites toward the redox reaction. In addition, formed amorphous MnO2 can also serve as a powerful catalyst to facilitate the redox couples of VO2+/VO2+ based on density functional theoretical (DFT) calculations. As a result, the VRFB using AMO@GF displayed an elevated energy efficiency and superior stability after 2400 cycles at 200 mA cm-2, and the maximum current density can reach 300 mA cm-2. Such a high-efficiency and convenient design strategy for the electrode material will drive the further development and industrial application of VRFBs and other flow battery systems.

Enhanced Atmospheric Water Harvesting Performance by Three-Dimensional Carbon Fiber Felt Structure.

Freshwater shortages and the uneven distribution of water resources are critical issues for economic development and human life, and collecting water vapor in the air is one of the important ways to alleviate these issues. In recent years, adsorption-based atmospheric water harvesting (AWH) techniques have received much attention, and the core difficulty in establishing an efficient system is to develop a highly efficient functional material for AWH. In this work, an AWH material was prepared consisting of carbon fiber felt as a three-dimensional skeleton and loaded with poly(vinyl alcohol) immobilized LiCl and graphite, as a water capture and release functional material. A 24 h water capture-3 h water release test was carried out at room temperature, showing excellent water collection ability of 0.907 g·g-1 of water at 30% relative humidity (RH) and 2.429 g·g-1 of water at 80% RH. Using a 2 h capture-2 h release cycling test, the sample demonstrated a stable water capture-release performance. An outdoor field test was conducted, showing water collection efficiencies of up to 60%. We believe that the carbon fiber felt can provide good mechanical properties and achieve a high mass loading of the functional materials, and the composite material has a simple manufacturing process and realizes energy saving and sustainable water harvesting.

In situ synthesis of carbon quantum dots on carbon felt fibers as a new solid-phase microextraction sorbent for chromatographic analysis of bisphenol A

In this study, an innovative and efficient solid − phase microextraction (SPME) sorbent was introduced based on carbon quantum dots (CQDs) modified carbon felt (CF) substrate. CF, due to its unique characteristics including high porosity, solvent durability (without swelling), and simple modification, it was proposed as an attractive platform for preconcentration purposes. To create an impressive adsorption capacity, the synergistic effects of CQDs and the carbonaceous structure of CF were profited off. CQDs were successfully synthesized on CF fibers by using an improved one-step hydrothermal method, and the resulting sorbent was referred to as CQDs@CF. Since bisphenol A (BPA) is an environmental toxin and can disrupt the endocrine system and potentially lead to cancer, highlighting the importance of detecting its presence. The prepared sorbent was used to extract bisphenol A (BPA) as a model compound from the real samples, followed by HPLC − UV analysis. Extraction parameters including desorption solvent type, and its volume, extraction, and desorption time, salting out effect and, solution pH were optimized. FESEM, EDX, FT − IR, and N2 adsorption–desorption were used to characterize the sorbent morphology, structure, and elemental contents. Under optimal conditions, the response linearity in the range of 0.05 − 500 ng mL−1 and detection limit at the level of 0.01 ng mL−1 were obtained. Additionally, the relative standard deviations (RSD) for newly prepared CQDs@CF (sorbent to sorbent repeatability) and a certain multi − used CQDs@CF (single sorbent repeatability) at a concentration of 100 ng mL−1 of BPA, were found to be 7.2 and 4.8, respectively.

Structural properties and barrier performance of low-cost aerogel composites for building insulation

The high cost and weak mechanical properties of silica-based aerogel seriously affect its wide application in the field of building insulation. In this paper, low-cost SiO2 aerogel (WSA) was prepared based on water glass/water system, and the modulation of aerogel network structure was achieved under the dual effect of sodium methylsilicate (SMS) and pH. WSA exhibits extremely low density (∼88.5 kg/m3) and thermal conductivity (0.02114 W/(m·K)) as well as high hydrophobicity (150°). The cost of WSA is 53 % lower compared to atmospheric pressure drying and 21.5 % lower than commercial aerogel. On this basis, rock wool fiber felt (RWF) and ultrafine glass fiber wool felt (UGFW) were modified with WSA. The effect of fiber arrangement on the force-thermal coupling property of WSA@RWF was investigated. Meanwhile, the addition of WSA reduced the volumetric water absorption of RWF by 85.1 % and 91.4 %. Since the sandwich structure, the thermal conductivity of WSA@UGFW can be as low as 0.01168 W/(m·W), which is 44.7 % and 44.4 % lower than that of UGFW and WSA. It features a low density of 45.7 kg/m3 and a high hydrophobicity angle of 155.87°. In addition, the compressive strength of WSA@UGFW is increased by 16.5 times. Therefore, the aerogel materials prepared in this paper have great application potential as fire-proof building insulation materials.

Bioinspired melt-blown fiber felt with flame retardancy for efficient oil spill remediation by solar-driven oil evaporation and adsorption

Confronted with rapid-spread river oil leaks and marine oil spills containing toxic and light fractions, conventional emergency response measures often fall short. This study proposes a solar-driven oil evaporation and adsorption (SOEA) strategy that efficiently addresses the challenges posed by toxic and light oils in rivers and oceans. Inspired by the self-protection and anti-fouling effects of fish scales, a photothermal oil-adsorbing felt with a biomimetic scale structure for efficient SEOA is constructed by decorating functional components onto the melt-blown fiber felt using scalable spraying technology. The rational integration of a dual-layer scale structure and functional constituents imparts stable superhydrophobicity, self-cleaning, flame retardancy, enhanced mechanical strength, and a higher oil adsorption capacity. Benefiting from the superior photothermal conversion, the solar-vapor conversion efficiency of the resulting P-EG/MXene@PP reaches 85.6 % under 1 sunlight, with an evaporation rate for light oil of 13.17 kg/m2/h, 8 times higher than natural volatilization. For crude oil floating on water, it achieves a 98 % oil removal efficiency in 6 h, with 41 wt% of the light fraction evaporated. This research provides distinctive insights into solar-driven oil spill remediation behavior and pioneers the SOEA strategy, offering rapid, efficient, and safe solutions for intricate oil spill scenarios.

Synergistically enhanced electromagnetic interference shielding and mechanical properties of epoxy resin composites with a preconstructed hierarchical structure

AbstractElectromagnetic interference (EMI) shielding materials have attracted extensive attention as highly integrated electronic devices generate large amounts of electromagnetic pollution. Here, PNF/NGx‐EP composites with excellent EMI shielding properties and superior flexural strength were reported, where nickel‐plated carbon fiber (NF) felts and NH2‐Graphene (NG) were adopted to pre‐construct a hierarchical structure within epoxy resin (EP). The macroscopic NF network constructed a continuous conductive pathway and the NG grafted on the surface of NF formed a second microscopic conductive network. Consequently, the PNF/NG0.5 felts exhibited a quite high electrical conductivity of 138.4 S/cm, and the PNF/NG0.5‐EP composites presented excellent EMI shielding effectiveness (EMI SE) (57.4 dB at 11.9 GHz). Intriguingly, the flexural strength of the NF/EP composites was enhanced after the incorporation of NG, which was attributed to the mechanical locking effect and covalent bonding. In summary, this approach reconciles the contradiction between EMI shielding properties and mechanical properties of EP composites, and allows them to be promisingly employed for EMI shielding and protection in aerospace, weaponry, and communications.Highlights A hierarchical structure of PNF/NGx felts was preconstructed within EP via Michael addition/Schiff base reaction. The PNF/NGx‐EP composites exhibited remarkable EMI shielding properties (57.4 dB) and superior flexural strength (137.0 MPa), which are expected to realize practical applications in EMI shielding.

High-purity rayon-based carbon fiber felt prepared by halogen gas purification for superior thermal insulation and oxidation resistance

High-purity rayon-based carbon fiber (CFRay) felt holds significant promise for applications in thermal protection systems and semiconductor crystal growth furnaces. This study employs halogen gas purification and high-temperature purification techniques in the fabrication of high-purity CFRay felt. Additionally, the influence of the purification process on the thermal insulation and oxidation resistance of CFRay felt is investigated. The glow discharge mass spectrometer analysis reveals that purification at a lower temperature of 2300 °C achieves a purity level of 6.9 ppm, surpassing both purified CFRay felt without halogen at 2300 °C (56.1 ppm) and high-temperature treated CFRay felt at 3000 °C (10.4 ppm). Thermal insulation and dynamic-static oxidation resistance tests show that the properties of CFRay felt are concurrently affected by the heat treatment temperature. Compared to high-temperature purification, halogen gas purification operates at lower temperatures, preventing the graphitization of CFRay, thereby ensuring high purity while enhancing thermal insulation and demonstrating relatively superior oxidation resistance. This study offers novel insights into the preparation and performance adjustment of high-purity CFRay felt.

Stress and temperature sensing in self-sensing flexible felt composite based on carbon fibers

Self-sensing composites based on carbon fibers (CFs) offer a wide range of remarkable properties, making them suitable for various significant industrial and engineering applications. In this study, the wet-laid method was employed to prepare flexible short carbon fiber felts (CFFs). The microstructure analysis was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. To exclude contact capacitance, the relative permittivity was measured using an LCR meter. The resistivity was measured through the four-probe method and a multimeter. We investigated the relationship between stress, temperature, and the dielectric and conduction behavior while also analyzing the underlying mechanisms behind the self-sensing phenomenon. The results indicate that for an areal density of 52.6 g/m2, the CFF exhibits a relative permittivity of 400, which is significantly lower than that of pitch-based carbon fiber. This disparity suggests that smaller crystallite sizes promote AC polarization. Additionally, both permittivity and conductivity increase with rising compressive stress and temperature, implying that compression and heating strengthen the dielectric and conduction behavior. The increase in polarization during compression is attributed to the enhanced polarization continuity, whereas the rise in conduction is attributed to the improved conduction connectivity. The rise in charged carriers induced by thermal energy leads to positive pyropermittivity and negative pyroresistivity. Notably, self-sensing in terms of permittivity is more pronounced compared to resistivity, suggesting that polarization is more sensitive to stress and temperature changes than conduction.

Preparation and thermal insulation performance of Al2O3[sbnd]Y2O3[sbnd]SiO2 ternary composite aerogels with high specific surface area and low density

Against the background of global energy shortages and the need for long-term flight safety of aerospace vehicles, traditional silica aerogels have the problems of insufficient temperature resistance and poor thermal insulation at high-temperatures, and are no longer able to meet the demand. In this study, a series of monolithic Al2O3Y2O3SiO2 ternary aerogels were successfully synthesized via synchronous sol–gel and ethanol supercritical drying. Both the prepared aerogels and the calcined samples at 1000 °C exhibited a complete three-dimensional network structure and a high specific surface area (up to 675.7 m2/g and 214.4 m2/g), which was attributed to the supporting effect of the Al2O3 component on the overall skeleton and the inhibiting effect of the Y2O3 component on the crystal transformation. Mullite fiber reinforced Al2O3Y2O3SiO2 aerogel composites were synthesized by vacuum impregnation using mullite fiber felt as a matrix. The prepared sample exhibit very low thermal conductivity (as low as 0.079 W⋅m−1·K−1 at 1000 °C). In summary, the good structural stability and high temperature thermal insulation performance make Al2O3Y2O3SiO2 ternary aerogel have the potential of efficient service in more application scenarios. This study provides a product optimization reference idea for the thermal insulation material industry.

Effect of stacking order on the properties of hybrid palm sheath/polyester fiber felt‐reinforced polymer composite laminates

AbstractNatural fiber‐reinforced composites exhibit excellent mechanical properties. However, achieving a balance between excellent mechanical properties and optimal acoustic performance remains a challenge. In this study, four composite laminates with different stacking orders were fabricated using polyester fiber mats (WFs) and palm sheaths (WPs) through a hot‐press process. Moreover, the effects of different stacking orders on the mechanical and acoustic properties of the composite were investigated. The results revealed that the incorporation of polyester fiber felts and the modification of the layup sequence of WP and polyester fiber felts significantly improved the mechanical and acoustic properties of the composites. Scanning electron microscopy images revealed a strong bonding between palm fibers and polyester fibers at the epoxy resin interface. Compared with pure palm fiber composites, the alternately stacked palm fibers and polyester fibers (WP/WP/WF/WP/WF) exhibited the highest mechanical properties, with a significant enhancement of 142.67% and 16.90% in flexural and tensile strengths, respectively. Additionally, the peak absorption coefficient of polyester fiber felts, positioned in the surface layer of the composite material, within the 2580–3400 Hz frequency band significantly increased from 0.07 to 0.44. Therefore, this study indicates that modifying the stacking order improves the mechanical and acoustic properties of the composites, making them suitable for use in acoustic engineering materials for buildings and decorative panels for furniture, including perforated panels and acoustic screens.Highlights The fabric‐like textured structure significantly enhanced the overall performance of the composites. The stacking order significantly influenced the overall properties of the composite. Alternately stacked polyester fiber felts and palm fibers exhibited excellent mechanical performance. The polyester fiber felts positioned on the surface layer of the composites exhibited superior mechanical performance. A laminate with “green” attributes and good acoustic properties was fabricated.

Morphological rationale for the application of titanium nickelide in reconstructive surgery of the diaphragm

Purpose of the study: to experimentally study the morphological features of the reaction of diaphragm tissue to porous titanium nickelide in comparison with medical felt.Materials and methods. A series of experiments was carried out on 20 rats. The animals were divided into two comparison groups: in the main group (n = 10), the reaction of diaphragm tissue to an implant made of titanium nickelide was studied; in the control group (n = 10), an implant made of medical felt (fluoroplastic-4) was used. Animals were removed from the experiment 14, 30, 60 and 90 days after surgery. A histological study of the reaction of the diaphragm tissue to the implant was carried out, as well as the structural behavior of the material under study.Results. Macroscopically, after 14 days in the main group, a local adhesive process was noted. In the long term, the implant was covered with a thin connective tissue film without signs of inflammation. In the control group, after 14 days, phenomena of inflammatory infiltration with organ involvement were observed. After 30 days, the inflammatory infiltrate persisted with the formation of a connective tissue capsule. The implant increased in size with deformation, swelling, and in the long term, disintegration of the structure. Histologically, on the 14th day in both groups, granulation tissue formed between the implant and the diaphragm. By the 30th day in the main group, the number and thickness of collagen fibers increased, they filled the porous structure of the material. In the control group, the appearance of giant multinucleated cells was noted between the felt fibers, which are indicators of the body's tissue reaction to foreign material. On the 60th day in the main group, a regenerate of mature connective tissue formed around the implant, filling the pores of the material and spreading to the muscle fibers of the diaphragm. In the control group, a picture of productive granulomatous inflammation with phenomena of biodegradation of the material was observed.Conclusion. The results of the experiment demonstrated the absolute advantage of titanium nickelide in reconstructive surgery of the diaphragm. At the same time, the disadvantages of using medical felt associated with the body’s reaction to the material as a foreign body and the tendency to resorption are noted.

Experimental investigation on temperature-dependent effective thermal conductivity of ceramic fiber felt

This paper presents a method to invert the effective thermal conductivity of ceramic fiber felt under high temperatures using experimentally measured specific heat capacity, density, and transient temperature data. The method combines the solution of the heat transfer equation with an inversion method based on real-valued genetic algorithm (GA) optimization, and 11 target parameters can be simultaneously inverted with one experimental dataset. The effective thermal conductivities of ceramic fiber felt were obtained by inversion under ambient pressures of 2 Pa and 100 kPa, compression ratios of 0.8–1.0, and temperature ranges of 295∼1273 K. The results indicates that the effective thermal conductivities of ceramic fiber felt derived from the inversion method are in concurrence with the outcomes of the steady state method. The effective thermal conductivities of the ceramic fiber felt range from 0.069 to 0.321 W m−1 K−1. It is observed that the effective thermal conductivity increases with higher temperature, and decreases with growing compression ratio. The impact of ambient pressure on effective thermal conductivity is linked to the level of compression.

Computation of effective thermal conductivity of carbon fiber felts through numerical simulation and development of reduced order models

One of the major drivers of heat transfer within a spacecraft heatshield is the effective thermal conductivity of the thermal protection material. For carbon-based thermal protection materials, this quantity is strongly connected to the thermal conductivity of the carbon fiber felt (preform) used to create the final composite. Use of effective thermal conductivity data from experiments in volume averaged numerical models is complex because: i) they are carried out in different media than its actual application, ii) changes on geometry or material properties require repetition of the experiments. Simulation of effective thermal conductivity using high fidelity simulations can overcome those problems. In this work, we propose a synthetic model based of the carbon fiber felt of Calcarb® using Porous Microstructure Analysis (PuMA) software. This model is first validated with available experimental data and applied to new experiments and to study the effect of pyrolysis gas mixture on the effective property. Simplified correlations are then developed, which predict with remarkable accuracy the effective thermal conductivity of the Calcarb® material. The developed model can be used to explore and predict effective conductivity at different conditions. In addition, the simplified algebraic correlations can be easily implemented in volume averaged material response codes to account in a more appropriate way for the effect of the percolating pyrolysis/atmospheric gas.

Enhanced Cu(II) Adsorption Capacity of Recyclable Activated Carbon Fibers for Flexible Self‐Supporting Electrodes in Capacitive Deionization

AbstractAs the cardinal part of capacitive deionization apparatus, the performance of electrode directly determines the capacitive deionization's adsorption rate, adsorption capacity and selectivity. However, the adsorptivity and reusability of electrode material for special adsorbate need to be developed urgently for the application of capacitive deionization in wastewater purification. In this research, we successfully enhanced the Cu(II) adsorptivity of activated carbon fiber felt (ACFF) to 23 mg/g (4.47 times of ACFF0) by the sonication‐assisted chemical reactivation process with the solution of 20 wt % NaOH used as activator (ACFF‐N20). As ACFF‐N20 used as cathode, the Cu(II) electro‐adsorptivity of ACFF‐N20 under a current of 0.15 A is 84 mg/g for 130 mg/L Cu(II) standard working fluid. For the Cu(II) wastewater with a concentration of 50 mg/L, it can be purified to 0.14 mg/L by one step of capacitive deionization, which below the drinking standard of World Health Organization. By the technology of low‐temperature pickling regeneration, the regeneration rates of ACFF‐N20 are 102 %–106 % for five recycling times of Cu(II) electrosorption process. Based on fitting analysis of adsorption processes using different kinetic models, it was found that Langmuir model is more convergent than Freundlich model to the adsorption isotherms. Additionally, Bangham adsorption kinetic model and pseudo‐first order adsorption kinetic model have the best fitting correlation for the Cu(II) static adsorption and electrosorption of ACFFs.

In Situ Ceramization of Nanoscale Interface Enables Aerogel with Thermal Protection at 1950 °C.

Conventional carbon fiber felt-reinforced aerogel composites are often used as lightweight thermal protection systems (TPSs) for aerospace craft. However, due to their poor oxidation resistance, they have gradually failed to handle increasingly harsh thermal environments. In this work, a nanoscale composite coating interface of SiC-ZrC ceramic precursor is first constructed on the fiber surface. Subsequently, using the coated fiber felt as a three-dimensional skeleton and through polymerization-induced phase separation, an aerogel composite with excellent thermal protection in extreme thermal environments is prepared. Owing to the in situ ceramization of this nanoscale interface at ultrahigh temperatures, the back temperature of the 12 mm thick aerogel is only 147 °C after exposure to an oxyacetylene flame at 1950 °C for 70 s. Meanwhile, the central region of the aerogel recedes by only 7%. Not only does this work provide a way to enhance aerogels by constructing a self-ceramizable nanoscale interface it is also expected that the developed aerogel composite can be applied in the ultrahigh-temperature thermal protection of future aerospace craft.

Bio-inspired polydopamine modification of recycled carbon fibers for improving the performance of recycled carbon fiber reinforced mortars

The hydrophobicity nature of the waste carbon fiber felt (WCF) surface results in the formation of a weak interface with the paste during the curing process of WCF concrete, which seriously affects the performance of WCF concrete and the reuse of WCF. To address this problem, this paper utilized polydopamine (PDA) for the functionalization of WCF to enhance bonding between WCF and paste. The wettability, Ca2+ complexation, and functional groups of PDA coating on WCF were analyzed by contact angle, ICP-OES, and XPS, respectively. Additionally, the effects of incorporating PDA-functionalized WCF on the flowability, compressive strength, hydration kinetics, pore structure, water absorption capillary, and SEM of mortars were tested. Experimental results showed that the PDA coating improved the wettability of WCF and enhanced the flowability of WCF mortar. What's more, the PDA coating could chelate Ca2+ and promote the formation and deposition of hydration products on the WCF surface, resulting in a denser interfacial transition zone (ITZ). Compared with ordinary WCF mortar, the compressive strength of the PDA-modified WCF mortar was increased by 18% at 28d. Furthermore, the capillary water absorption of the modified group mortar was also decreased by up to 13%, significantly enhancing the durability of mortars. This paper presents a green and simple bio-inspired method to strengthen the ITZ between WCF and paste, which is fundamentally different from the traditional modification methods, and also offers a theoretical basis and technical foundation for the sustainable utilization of WCF.