Abstract
The growing demand for advanced energy storage devices with high energy density and high safety has continuously driven the technical upgrades of cell architectures as well as electroactive ...materials. Designing thick electrodes with more electroactive materials is a promising strategy to improve the energy density of lithium‐ion batteries (LIBs) without alternating the underlying chemistry. However, the progress toward thick, high areal capacity electrodes is severely limited by the sluggish electronic/ionic transport and easy deformability of conventional electrodes. A self‐supported ultrahigh‐capacity and fire‐resistant LiFePO
4
(UCFR‐LFP)‐based nanocomposite cathode is demonstrated here. Benefiting from the structural and chemical uniqueness, the UCFR‐LFP electrodes demonstrate exceptional improvements in electrochemical performance and mass loading of active materials, and thermal stability. Notably, an ultrathick UCFR‐LFP electrode (1.35 mm) with remarkably high mass loading of active materials (108 mg cm
−2
) and areal capacity (16.4 mAh cm
−2
) is successfully achieved. Moreover, the 1D inorganic binder‐like ultralong hydroxyapatite nanowires (HAP NWs) enable the UCFR‐LFP electrode with excellent thermal stability (structural integrity up to 1000 °C and electrochemical activity up to 750 °C), fire‐resistance, and wide‐temperature operability. Such a unique UCFR‐LFP electrode offers a promising solution for next‐generation LIBs with high energy density, high safety, and wide operating‐temperature window.
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•Lightweight polybenzoxazine (PBz) aerogels were fabricated by hexamethylene diisocyanate (HDI) modification.•The introduction of HDI formed a covalent-crosslinked structure with the ...chemical structure of the PBz aerogel.•The HDI-modified PBz aerogel demonstrates a self-extinguishing time of less than 1 s after removal from a 1200 °C flame.
The rapid advancement of modern industries has imposed demands on thermal insulators that possess not only low thermal conductivities but also multifunctional properties. Polybenzoxazine (PBz) aerogels with several advantages have garnered considerable research interest in recent years. Nevertheless, PBz aerogels acquired from ambient pressure drying still confront the challenge of exhibiting relatively high densities and thermal conductivities. In this study, to enrich the category and propose practical ideas for overcoming the above plight, hexamethylene diisocyanate (HDI) was selected as an additive to prepare lightweight and efficient thermal-insulating PBz aerogels through chemical modification. Compared with the pristine specimens (0.268 g·cm−3, 0.0387 W·m−1·K−1), the HDI-modified PBz aerogels exhibited lower densities (0.237–0.256 g·cm−3) and thermal conductivities (0.0354–0.0370 W·m−1·K−1). Moreover, the introduction of HDI has been demonstrated to not impact their superior intrinsic flame retardance, despite an observed reduction in the residual char yields in the HDI-modified groups. Given these excellent properties, PBz-HDI aerogels are expected to be promising candidates for thermal insulation and fire resistance applications.
The study is centered on optimizing graphene oxide (GO) concentration in M30 designer mix concrete, aiming to enhance its performance under elevated temperatures and fire conditions. The findings ...revealed a significant 40 % increase in compressive strength with the addition of 0.05 wt% GO to M30 grade concrete after 28 days of curing in water. GO played a crucial role in mitigating the impact of high temperatures under heating in furnace and fire exposure under flame, resulting in reduced crack formation and a delayed temperature rise during thermal loading. In heat resistance assessments, GO concrete exhibited a substantial delay in temperature rise compared to plain concrete under controlled furnace conditions, showcasing superior resistance to elevated temperatures. Thermogravimetric analysis and Differential TG analysis elucidated the superior retention of water and hydrated products in GO concrete, even after exposure to high temperatures. Fire exposure tests demonstrated that GO concrete exhibited a much lower surface temperature (less than 50 °C) opposite to the flame (flame temperature ∼ 700 °C) within a 15 cm width of concrete. Additionally, fewer and less severe cracks appeared in the GO concrete compared to plain concrete, showcasing its anti-spalling behavior. The altered matrix porosity of GO concrete, creating nano- and microscale channels, contributed to reduced vapor pressure and mitigated crack formation. This comprehensive study underscores the potential of GO as a versatile additive in concrete, offering enhancements in strength, heat resistance, and fire performance for sustainable and resilient infrastructure development.
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•0.05 wt% GO added M30 grade concrete showed 40 % increase in compressive strength.•GO concrete exhibited a substantial delay in temperature rise compared to plain concrete.•Heat treated GO concrete showed superior retention of water and hydrated products.•15 cm thick GO concrete exhibited much lower surface temperature (∼ 50 °C) under flame.
•Preparation of non-toxic, lightweight and fire-resistant EMI shielding aerogel.•Such aerogels are fabricated by freeze-drying method.•High SSE/t value (5729 dB cm2 g−1) exceeds many other reported ...porous materials.
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Rapid growing of electronics has not only caused severe electromagnetic wave pollution, but also created a risk of fire and explosion. Therefore, developing ultralight, fire-resistant, high-performance electromagnetic interference (EMI) shielding materials are imperative but also challenging. Considering the outstanding metallic conductivity and high aspect ratio, 2D Ti3C2Tx has been reported to be one of the most promising candidates for exhibiting excellent EMI shielding performance. Herein, we demonstrate a facile method to fabricate cellulose nanofiber (CNF)/ammonium polyphosphate (APP)/Ti3C2Tx composite aerogels via a simple freeze-drying method. The resultant CNF/APP/Ti3C2Tx composite aerogels exhibited excellent fire-resistance without obvious shrinkage when placed over the flame of an alcohol burner. Besides, the 8-mm-thick composite aerogel with 60% of Ti3C2Tx showed an average EMI shielding effectiveness of 55 dB (specific EMI shielding effectiveness/thickness could be ~5729 dB cm2 g−1) with an absorption-dominant mechanism. This performance is owing to the relative high electrical conductivity (12 S/m) and multiple reflections from the porous structure. These characteristics make the composite aerogel a much more competitive product for a high-performance EMI shielding material.
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•Phosphorus-containing metal complexes (CePn) tunable morphologies are synthesized.•The addition of 4 wt% of CePn reduces the peak heat release rate of the PC by 46%.•A desired ...UL-94 V-0 rating and a LOI value of 27.3% are achieved.•The PC/CePn-4.0 maintains a high transparency of 90.1%.•The PC/CePn-4.0 exhibits superior thermostability to previous counterparts.
It has been desirable to create flame retardant, transparent polycarbonate (PC) materials while retaining high thermostability and mechanical strength to meet its practical applications in the electrical, optical lighting, automobile and mobile fields. Unfortunately, current flame retardants offer satisfactory flame retardancy at the expense of other properties because of improper designs. For this reason, it has remained a grand challenge to achieve an integrated performance portfolio. Herein, we report rod-like phosphorus-containing metal complex aggregates (CePn) by one-step solvothermal method. The results show that the peak heat release rate (PHRR) and total smoke release (TSR) of the bulk PC are respectively reduced by 46% and 26% in the addition of 4 wt% of CePn, in addition to a desired UL-94 V-0 rating and a limiting oxygen index (LOI) of 27.3% because of dual-phase flame retardant mechanisms of CePn. Moreover, the final PC maintains a high transparency of 90.1% and a comparable tensile strength to the bulk PC. Moreover, the final PC composite shows enhanced thermal stability noticeably which is superior to that of any other reported systems. This work offers an innovative methodology for the design of flame retardants with tunable aggregated morphologies, and the creation of high-performance PC composites combining exceptional flame retardancy, transparency, thermostability and mechanical strength.
With the prevailing energy challenges and the rapid development of aerospace engineering, high-performance thermal insulators with various functions are attracting more and more attention. Ceramic ...aerogels are promising candidates for thermal insulators to be applied in harsh environments because of their low thermal conductivity and simultaneously excellent thermal and chemical stabilities. In general, the effective properties of this class of materials depend on both their microstructures and the intrinsic properties of their building blocks. Herein, to enrich the family and broaden the application fields of this class of materials, we prepared ultralight α-Si
N
nanobelt aerogels (NBAs) with tunable densities ranging from 1.8 to 9.6 mg cm
. The α-Si
N
NBA realized resilient compressibility (with a recoverable strain of 40-80%), fire resistance (1200 °C butane blow torch), thermal insulation (0.029 W m
K
), and electronic wave transparency (a dielectric constant of 1-1.04 and a dielectric loss of 0.001-0.004) in one material, which makes it a promising candidate for mechanical energy dissipative, fire-resistant, and electronic wave-transparent thermal insulator to be applied in extreme conditions. The successful preparation of such resilient and multifunctional α-Si
N
NBAs will open up a new world for the development and widespread applications of ceramic aerogels.
•The bonding performance of geopolymer paste after exposure to elevated temperatures was quantified.•The thermal behavior of geopolymer paste at fire conditions was evaluated.•The mass loss in ...geopolymer samples induced by elevated temperatures was evaluated.•Microstructural changes for the geopolymer specimens after heating treatment was investigated.
Geopolymers are generally agreed to provide good steel-to-concrete bonding performance and fire resistance. However, few previous studies on geopolymer investigated the steel-to-concrete bonding behavior and fire-resistance at very high temperatures (>800 °C), hence cannot reveal the damage of a severe fire accident. This paper presents the results of an extensive experimental study carried out to investigate the effect of elevated temperature on the thermal-physical behaviors and mechanical properties of fly ash-based geopolymer paste. After being exposed up to 1200 °C according to the RATB fire curve, the damage stages of geopolymer paste (GPC) and ordinary Portland cement (OPC) were investigated through the unconfined compressive strength test, push-out test, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM) analysis. Based on the results and existing literature, there was a less mass loss and a better compressive strength for GPC paste after the treatment, which led to a better bonding behavior of GPC compared with OPC paste. In addition, a positive linear relationship between the bond strength and the compressive strength was found for both GPC and OPC. Furthermore, the stable properties of phases change and porous micro-structure in GPC identified by SEM and XRD methods were important for a better bond behavior at elevated temperatures. Thus, the GPC offers a feasible alternative to OPC in practical fire-resistant building applications.
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•Novel aerogels with chemically and physically double cross-linked networks were fabricated.•The aerogel showed ultrahigh compressive modulus of 41.9 MPa.•The aerogel maintained high ...modulus at high temperatures.•The aerogel showed excellent fire resistance and high-temperature thermal insulation.
Aerogels with low density and excellent thermal insulation are seriously plagued by poor mechanical properties with low compressive moduli in the kPa range, especially in extreme conditions such as high temperatures and fires. In this work, a new double chemical cross-linking and physical cross-linking strategy is developed to synthesize ultrahigh-modulus aerogels with extreme-condition resistance from low-cost polyvinyl alcohol (PVA), bio-based phytic acid (PA) and montmorillonite (MMT). The resultant aerogels consist of interpenetrating networks with chemically cross-linked domains between PVA and PA and physically cross-linked domains among PVA, PA and MMT, leading to an ultrahigh compressive modulus of 41.9 MPa and a specific modulus of 455.4 MPa·cm3·g−1, which can even withstand a car crush. Benefitting from the formation of ultra-strong network backbones containing phosphorus and clay, the aerogels amazingly show excellent fire resistance and high-temperature thermal insulation features. This robust porous material can maintain its structural integrity and high modulus (~2 MPa) after exposure to extremely high-temperature flame (~1300 °C), and also exhibits high mechanical modulus of ~4 MPa after heating treatment at 900 °C. These special characteristics make the aerogel a promising insulation candidate in the fields of aviation, aerospace and other applications.
Justification of impregnation modes for wood Gazizov, A M; Samosenko, E G; Popova, E V
Journal of physics. Conference series,
07/2021, Letnik:
1967, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
One of the most significant disadvantages of wood materials is increased combustibility. Therefore, the problem of reducing the combustibility of wood materials is relevant. The article ...describes an experimental study of impregnation of wood using biopiren MIG-09, which is a hybrid composition on a salt basis with the addition of functional substances of non-salt nature, at different temperature regimes. Two stages of the study were chosen for the experiment. The optimum temperature regimes for different methods of applying the composition to increase the fire resistance of wood were established experimentally. Also fire tests were carried out to analyze the degree of penetration of the solution.
Fire resistance is a key advantage of geopolymer (GP) materials. While most research focuses on alkali-activated GPs, this study examines the fire resistance of phosphoric acid-activated GPs with ...varying phosphorus-to-aluminum (P/Al) molar ratios. By activating metakaolin with different ortho-phosphoric acid (H3PO4) solutions, it was found that GPs with P/Al > 0.59 exhibited intumescence during fire tests, resulting in a 110 °C lower backside temperature (310 °C) compared to non-intumescent GPs (420 °C). Physico-chemical changes were analyzed before and after fire tests using DMA, TGA NMR, EPMA, and XRD. The study revealed dehydration, crystallization, and rheological changes, with NMR showing transitions from Al(VI) to Al(IV), full condensation of phosphorus species, and Si-O-Al to Si-O-Si bonds. Intumescence was linked to GP softening between 100 and 160 °C, achievable only with a P/Al ratio ≥ 0.74, with no additional benefits from excess phosphorus.
•Acid-based intumescent geopolymers have been studied for the first time for fire protection.•Excellent thermal barrier effect of intumescence GP is observed for P/Al > 0.59.•A crystal phase of AlPO4 is formed under fire.•Solid-state NMR reveals that geopolymers are softening due to structural reorganization.
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