Mechanically Flexible Carbon Aerogel with Wavy Layers and Springboard Elastic Supporting Structure for Selective Oil/Organic Solvent Recovery

Biomimetic biomass-based composite carbon aerogels with excellent mechanical performance for energy storage and pressure sensing in extreme environments

The poor mechanical properties of biomass-based carbon aerogels after carbonization severely limit their application in pressure sensing and energy storage for wearable devices and electronic skin. In this work, a supramolecular assembly structure was designed inspired by the unique microstructure of natural wood for the preparation of biomass-based carbon aerogels with supercompressibility, elasticity, stable strain electrical signal response, and wide sensitive detection. Bacterial cellulose and lignin were selected as the main components of the biomass-based composite aerogel 'cell wall'. The graphene oxide with an aromatic structure was introduced to induce the assembly of firmly attached lignin and bacterial cellulose. The prepared biomass-based carbon aerogels exhibit supercompressibility (at least 100 cycles at 90 % strain), high elasticity (88.88 % height retention after 1000 cycles at a strain of 50 %), surprising temperature-constant superelasticity and fatigue resistance (shape retention rate greater than 85 %) at -196 ℃. In particular, it exhibits temperature-invariant high linear sensitivity over an extremely wide operating pressure range (0-43 kPa), allowing accurate detection of human signals. In addition, the prepared carbon aerogels exhibit excellent performance in supercapacitors. It has a specific capacitance of 158F/g at a current density of 1 A/g and an energy density of 18.75 Wh/kg at a high power density of 2500 W/g. This strategy also demonstrates its promise as a wearable device in hostile environments.

Enhancing Water Lubrication in UHMWPE Using Mesoporous Polydopamine Nanoparticles: A Strategy to Mitigate Frictional Vibration

Establishing a persistent lubrication mechanism and a durable tribo-film on contact surfaces is identified as crucial for improving the tribology and vibration characteristics of polymer materials under water-lubricated conditions. This study focuses on enhancing tribological performance and reducing frictional vibrations in ultrahigh molecular weight polyethylene (UHMWPE) through the incorporation of mesoporous polydopamine (MPDA) nanoparticles. In the experiments, MPDA nanoparticles were synthesized and blended with UHMWPE to create UHMWPE/MPDA composites. The interactions between these composites and zirconia (ZrO2) ceramic balls under water lubrication were examined. The results show that when the MPDA content of the composite is 1.5 wt %, the coefficient of friction and wear rate are reduced by 40% and 52% compared with those of pure UHMWPE, respectively. This notable enhancement helped to mitigate friction-induced vibrations, particularly those caused by intermittent sticking and slipping motions. MPDA nanoparticles were shown to act as reservoirs for water, releasing and replenishing water based on the loading conditions, which sustained continuous water-based lubrication at the composite surfaces. Additionally, the surface deformation behavior of the composite material is significantly weakened, which provides a more stable friction surface. This work introduces a novel approach to enhance the interface stability of polymers in water-lubricated environments, offering guidance for developing advanced materials and reducing friction and wear in engineering applications.

Highly Aligned Graphene Aerogels for Multifunctional Composites

Stemming from the unique in-plane honeycomb lattice structure and the sp2 hybridized carbon atoms bonded by exceptionally strong carbon-carbon bonds, graphene exhibits remarkable anisotropic electrical, mechanical, and thermal properties. To maximize the utilization of graphene's in-plane properties, pre-constructed and aligned structures, such as oriented aerogels, films, and fibers, have been designed. The unique combination of aligned structure, high surface area, excellent electrical conductivity, mechanical stability, thermal conductivity, and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions, enabling advancements in diverse fields. This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites. It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively. The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties, showing enhanced electrical, mechanical, and thermal properties along the alignment at the sacrifice of the perpendicular direction. This review showcases remarkable properties and applications of aligned graphene aerogels and their composites, such as their suitability for electronics, environmental applications, thermal management, and energy storage. Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

Sustainable and Scalable Synthesis of 2D Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitor

2D carbon nanomaterials such as graphene, carbon nanosheets, and their derivatives, representing the emerging class of advanced multifunctional materials, have gained great research interest because of their extensive applications ranging from electrochemistry to catalysis. However, sustainable and scalable synthesis of 2D carbon nanosheets (CNs) with hierarchical architecture and irregular structure via a green and low-cost strategy remains a great challenge. Herein, prehydrolysis liquor (PHL), an industrial byproduct of the pulping industry, is first employed to synthesize CNs via a simple hydrothermal carbonization technique. After mild activation with NH4 Cl and FeCl3 , the as-prepared activated CNs (A-CN@NFe) display an ultrathin structure (≈3 nm) and a desirable specific surface area (1021 m2 g-1 ) with hierarchical porous structure, which enables it to be both electroactive materials and structural support materials in nanofibrillated cellulose/A-CN@NFe/polypyrrole (NCP) nanocomposite, and thus endowing nanocomposite with impressive capacitance properties of 2546.3 mF cm-2 at 1 mA cm-2 . Furthermore, the resultant all-solid-state symmetric supercapacitor delivers a satisfactory energy storage ability of 90.1 µWh cm-2 at 250.0 µW cm-2 . Thus, this work not only opens a new window for sustainable and scalable synthesis of CNs, but also offers a double profits strategy for energy storage and biorefinery industry.

Natural microfibrils/regenerated cellulose-based carbon aerogel for highly efficient oil/water separation

Cellulose-based carbon aerogels as biodegradable and renewable biomass materials have presented potential applications in oil/water separation. Herein, a novel carbon aerogel composed of natural microfibrils/regenerated cellulose (NM/RCA) was directly prepared by economical hardwood pulp as raw material using a novel co-solvent composed of deep eutectic solvent (DES) and N-methyl morpholine-N-oxide monohydrate (NMMO·H₂O). In addition, the morphology and structure of the filiform natural microfibers could be remained after carbonized at 400 ℃, which resulted in a low density (8-10 mg cm^-3), high specific surface area (768.89 m² g^-1) and high sorption capability. In addition, the aerogel exhibited high compressibility, outstanding elasticity, excellent fatigue resistance, and recyclability (80.5% height recovery after repeating 100 cycles at the strain of 80%). Due to the morphology and composition of the carbonized microfiber surface, the superhydrophobic materials with a water contact angle of 151.5°, could sorb various oils and organic solvents with 65-133 times its own weight and maintain 91.9% sorption capacity after 25 cycles. In addition, the aerogels could achieve the continuous separation of carbon tetrachloride (CCl₄) from water with a high flux rate of 11,718.8 L m^-2 h^-1. Therefore, our prepared NM/RCA aerogels are anticipated to have broad potential applications in oil purification and contaminant remediation.

Sustainable and Elastic Carbon Aerogel by Polydimethylsiloxane Coating for Organic Solvent Absorption and Potential Application for Sensors (Infections, Environmental, Wearable Sensors, etc.)

Carbon aerogel is a promising material in various applications, such as water treatment, insulators, catalysts, and sensors, due to its porosity, low density, conductivity, and good chemical stability. In this study, an inexpensive carbon aerogel was prepared through lyophilization and post-pyrolysis using waste paper. However, carbon aerogel, in the form of short belts, is randomly entangled without a crosslinking agent and has weak mechanical properties, thus limiting its applications, which would otherwise be various. In this paper, a novel strategy is proposed to fabricate a PDMS-coated carbon aerogel (Aerogel@PDMS). Benefiting from microwave heating, precise PDMS coating onto the carbon frame was able to be carried out in a short amount of time. PDMS coating firmly tied the carbon microstructure, maintaining a unique aerogel property without blocking its porous structure. FE-SEM, RAMAN, XPS, and FT-IR were all used to confirm the surface change in PDMS coating. Compressible stability and water contact angle measurement showed that Aerogel@PDMS is a perspective organic solvent absorbent due to its good resilience and its hydrophobicity, and, as a result, its organic solvent absorption capacity and repeated absorption were evaluated, ultimately suggesting a promising material in oil clean-up and pollution remediation in water. Based on our experimental results, we identified elastic carbon aerogels provided by a novel coating technology. In the future, then, the developed carbon/PDMS composite can be examined as a promising option for various applications, such as environmental sensors, virus sensors, and wearable sensors.

Multifunctional microwave absorption materials of multiscale cobalt sulfide/diatoms co-doped carbon aerogel

Microwave absorption materials (MAMs) have attracted much attention for their potential applications in stealth technology and prevention of electromagnetic pollution problems. Multifunctional MAMs are highly demanded because they can be applied in harsh environments. Hence, based on multiscale manipulation of atomic engineering, nanostructure and microstructure, a multiscale hollow cobalt sulfide/diatoms co-doped carbon aerogel was preparedthrough the physical crosslinking of divalent ions, unidirectional freezing, kirkendall effect, and heteroatomic doping. The aerogel with a low density of 13.1 mg/mm³ has a unique "lamellar-pillar" network structure due to the growth of ice crystals during the preparation process. With the assistance of thiourea, the doping of N, S atoms and the construction of hollow cobalt sulfide are accomplished simultaneously. The ingenious integration facilitates the synergistic effect of conductive loss, defect polarization, interfacial polarization, and multiple scattering. The multiscale hollow cobalt sulfide/diatoms co-doped carbon aerogel had a maximum reflection loss of -51.96 dB and an effective absorption bandwidth of 6.4 GHz, which is higher than that of other reported MAMs. It is further verified through finite element simulation and experiments that the aerogel has an excellent microwave absorption properties. In addition, the aerogel has excellent thermal insulation and flame retardant properties. Therefore, the development of this aerogel can help to use MAMs in complex applications.

A Review of Graphene-Based Materials/Polymer Composite Aerogels

The fabrication of composite materials is an effective way to improve the performance of a single material and expand its application range. In recent years, graphene-based materials/polymer composite aerogels have become a hot research field for preparing high-performance composites due to their special synergistic effects in mechanical and functional properties. In this paper, the preparation methods, structures, interactions, properties, and applications of graphene-based materials/polymer composite aerogels are discussed, and their development trend is projected. This paper aims to arouse extensive research interests in multidisciplinary fields and provide guidance for the rational design of advanced aerogel materials, which could then encourage efforts to use these new kinds of advanced materials in basic research and commercial applications.

Cleanup of oils and organic solvents from contaminated water by biomass-based aerogel with adjustable compression elasticity

Leakage of oils and organic solvents poses a significant threat to aquatic environments. Here, low-temperature carbonized aerogels with highly porous and anisotropic structures obtained only from biomass-derived materials were proposed to absorb polymorphic oils from contaminated water. Specifically, carbonized aerogels prepared at temperatures of 300 °C and 350 °C exhibited ultra-high absorption capacities (40‒125 g g^-1) and oil-water separation efficiencies (> 99%) even in harsh environments, which were attributed to their exceptional properties, including high porosity, abundant macropores, excellent thermal stability, and hydrophobicity. Through citric acid crosslinking and low-temperature carbonization, the aerogels exhibited superior compression elasticity and could be cyclically utilized through simple extrusion while realizing the recovery of oils. Moreover, the outstanding photothermal conversion properties obtained through carbonization contributed to the high temperature and fluidity of the oils surrounding the aerogels, which is crucial for improving the absorption performance of high-viscosity oils. Such absorbent materials are used to separate crude oil from oil-water mixtures, which can achieve maximum absorption of 56 g g^-1 and increase the absorption rate (from several days to 10 min) in a low-temperature (4 °C) seawater environment.

Mechanically strong nanopapers based on lignin containing cellulose micro- and nano-hybrid fibrils: Lignin content-fibrils morphology-strengthening mechanism

Lignin-containing cellulose nanopapers are emerging multifunctional materials in the fields of coatings, films, and packaging. However, the forming mechanism and properties of nanopapers with various lignin content have not been thoroughly studied. In this work, a mechanically strong nanopaper was fabricated based on lignin-containing cellulose micro- and nano-hybrid fibrils (LCNFs). The influence of lignin content and fibrils morphology on the formation process of nanopapers was investigated to understand the strengthening mechanism of nanopapers. LCNFs with high lignin content provided nanopapers with intertwined micro- and nano-hybrid fibrils layers with small layer spacing, while LCNFs with low lignin content offered nanopapers interlaced nanofibrils layers with large layer spacing. Although lignin was expected to interfere with hydrogen bonds between fibrils, the uniformly distributed lignin contributed to the stress transfer between fibrils. Due to the good coordination between microfibrils, nanofibrils and lignin (as network skeleton, filler and natural binder, respectively), the well-designed LCNFs nanopapers with lignin content of 14.5 % showed excellent mechanical properties, including tensile strength (183.8 MPa), Young's modulus (5.6 GPa) and elongation (9.2 %). This work deeply reveals the relationship between lignin content, morphology and strengthening mechanism of nanopapers, and providing theoretical guidance for employing LCNFs as structural and reinforcing materials to design robust composites.

Selective Removal of Boron from Aqueous Solutions Using ECH@NGM Aerogels with Excellent Hydrophilic and Mechanical Properties: Performance and Response Surface Methodology Analysis

The remediation of environmental boron contamination has received extensive research attention. The adsorbent ECH@NGM aerogel with high hydrophilic and mechanical properties was synthesized to remove boron. The ECH@NGM aerogel had a high adsorption capacity of 81.11 mg/g, which was 14.50% higher than that of commercial boron-selective resin Amberlite IRA743. The Freundlich model and pseudo-second-order model described the adsorption behavior well. In addition, the response surface methodology (RSM) could predict the experimental outcomes and optimize the reaction conditions, and X-ray photoelectron spectroscopy (XPS) and control tests were utilized to investigate probable adsorption mechanisms. These data showed that the B ← N coordination bond was the primary adsorption force. The adsorbent had good resistance to interference from coexisting salts, high reusability, good adsorption performance even after five reuse cycles, and a high desorption rate in a relatively short time. The adsorption performance in real brines could be maintained at 80%. Therefore, this work not only provided ECH@NGM aerogels for the removal of boron from brine but also elucidated the main adsorption processes between N-containing adsorbents and boron, facilitating the design of future adsorbents for boron removal.

Carbon aerogels derived from waste paper for pipette-tip solid-phase extraction of triazole fungicides in tomato, apple and pear

In order to develop environmentally friendly, economical and facile preparation method of carbon aerogels (CAs), the waste printing paper as the raw material was combined with graphene oxide and carboxylic multi-walled carbon nanotubes to produce CAs (ρ = 44 mg cm^-3). The CAs with different composition were investigated, the addition of graphene oxide led to the reduction of adsorption sites and the reduction of extraction performance. But the carbon nanotubes made CAs have a better pore structure. The CAs as adsorbent were loaded into a pipette-tip for solid-phase extraction of hexaconazole and diniconazole. Coupled with gas chromatography, an analytical method was established under the optimized conditions. The limits of detection were between 0.08 and 0.32 mg kg^-1, the linear ranges were 0.96-200.0 mg kg^-1 and 0.24-200.0 mg kg^-1. The relative recoveries were in the range of 81.0-119%. The results indicated that the method had potential application for the determination of triazole fungicides.

Advanced cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) aerogels: Bottom-up assembly perspective for production of adsorbents

The most common and abundant polymer in nature is the linear polysaccharide cellulose, but processing it requires a new approach since cellulose degrades before melting and does not dissolve in ordinary organic solvents. Cellulose aerogels are exceptionally porous (>90 %), have a high specific surface area, and have low bulk density (0.0085 mg/cm³), making them suitable for a variety of sophisticated applications including but not limited to adsorbents. The production of materials with different qualities from the nanocellulose based aerogels is possible thanks to the ease with which other chemicals may be included into the structure of nanocellulose based aerogels; despite processing challenges, cellulose can nevertheless be formed into useful, value-added products using a variety of traditional and cutting-edge techniques. To improve the adsorption of these aerogels, rheology, 3-D printing, surface modification, employment of metal organic frameworks, freezing temperature, and freeze casting techniques were all investigated and included. In addition to exploring venues for creation of aerogels, their integration with CNC liquid crystal formation were also explored and examined to pursue "smart adsorbent aerogels". The objective of this endeavour is to provide a concise and in-depth evaluation of recent findings about the conception and understanding of nanocellulose aerogel employing a variety of technologies and examination of intricacies involved in enhancing adsorption properties of these aerogels.

Fabrication of Janus-type nanocomposites from cellulose nanocrystals for self-healing hydrogels' flexible sensors

Janus bio-nanomaterials have great application potential in functional solid surfactants, probes and flexible sensors. In this manuscript, the sustainable Janus cellulose nanocrystals-type (CNCs-type) nanomaterials were prepared by Pickering emulsion template method. The asymmetric functionalism of Janus nanorods was realized by asymmetrically grafting polypyrrole (PPy) and polydopamine (PDA) onto different sides of CNCs (Janus CNCs-PPy /PDA (JCNs)). JCNs was successfully applied to self-healing nanocomposite hydrogels and further applied to the development of flexible sensors. The self-healing efficiency of nanocomposite hydrogels was 87.2%, and the stress and strain reached 3.50 MPa and 453.45%, respectively. It is worth noting that flexible sensors have been widely used in the field of wearable electronic sensing for real-time monitoring of human movement due to their high sensitivity (gauge factor (GF) = 9.9) and fast response time (260 ms).

Synergistic Regulation of the Microstructure for Multifunctional Graphene Aerogels by a Dual Template Method

The performance of graphene aerogels (GAs) is based on the microstructure. However, GAs face a challenge of simultaneously controlling the size and alignment of pores strategically. Herein, we initially proposed a simple strategy to construct GAs with an adjustable structure based on the emulsion and ice dual template methods. Specifically, GAs with a honeycomb structure prepared by conventional freezing (CGAs) exhibited a high specific surface of 176 m²/g, superelasticity with a compressive strain of 95%, isotropic compression and thermal insulation performances, as well as an excellent absorption capacity of 150-550 g/g. Instead, the GAs with a bamboo-like network frozen by unidirectional freezing (UGAs) showed anisotropy in compression and thermal insulation behavior. Furthermore, UGAs exhibited incredible special stress (7.9 kPa cm³/mg) along the axial direction twice than that of the radial direction. Meanwhile, the apparent temperature of UGAs was only 45.6 °C when placed on a 120 °C hot stage along the radial direction. Remarkably, the properties of CGAs and UGAs were significantly improved with the adjustment of the microstructure.