Cellulose Nanofiber Aerogels Research Articles

Low-Cost Hyperelastic Fuller-Dome-Structured Nanocellulose Aerogels by Dual Templates for Personal Thermal Management.

It is critically important to maintain the body's thermal comfort for human beings in extremely cold environments. Cellulose nanofibers (CNF)-based aerogels represent a promising sustainable material for body's heat retention because of their renewability and low thermal conductivity. However, CNF-based aerogels often suffer high production costs due to expensive CNF, poor elasticity and/or unsatisfactory thermal insulation owing to improper microstructure design. Here, a facile dual-template strategy is reported to prepare a low-cost, hyperelastic, superhydrophobic Fuller-dome-structured CNF aerogel (CNF@PU) with low thermal conductivity. The combination of air template by foaming process and ice template enables the formation of a dome-like microstructure of CNF@PU aerogel, in which CNF serves as rope bars while inexpensive polyurethane (PU) acts as joints. The aerogel combines ultra-elasticity, low thermal conductivity (24mW m-1 K-1), and low costs. The as-prepared CNF@PU aerogel demonstrates much better heat retention than commercial thermal retention fillers (e.g., Flannelette and goose down), promising its great commercial potential for massively producing warming garments. This work provides a facile approach for creating high-performance aerogels with tailored microstructure for effective personal thermal management.

Cellulose nanofiber aerogels: effect of the composition and the drying method

Highly porous and lightweight aerogels of cellulose nanofibers (CNFs) have emerged as a promising class of material. This study delves into the impact of the composition (lignocellulose nanofibers–LCNFs and CNFs) and the drying methods (supercritical drying and freeze-drying) on the morphology and the properties of nanocellulose-based aerogels. The investigation evaluates the concentrations of nanofibers and the influence of lignin, a constituent of LCNFs recognized for enhancing the rigidity of plant cell walls, on the aerogel’s properties. The shrinkage rates, density, pore structure, and mechanical properties of the obtained aerogels are comprehensively compared. Supercritical drying proves advantageous for aerogel formation, resulting in materials with lower density and higher surface area than their freeze-dried counterparts at each concentration level. The use of acetone for supercritical drying contributes to reduce the shrinkage rates compared to ethanol. This decrease is attributed to the formation of a more rigid hydrogel during solvent exchange. Freeze-drying exhibits the lowest shrinkage rates and relatively higher porosity. The presence of lignin in the nanofibers influences the microstructure, yielding smoother and thicker pore walls. This study contributes to the comprehensive understanding of the intricate factors shaping nanocellulose aerogel properties, paving the way for the development of innovative and environmentally-friendly materials.

Low cost Non freeze-drying construction strategy of cellulose aerogels for efficient solar desalination

Aerogel-like materials with three-dimensional pore structures show great potential in the field of efficient solar-driven interfacial evaporation by virtue of their fast water transport as well as efficient energy confinement properties. However, the preparation of aerogels is currently limited by high-cost strategies such as freeze drying or supercritical drying. Here, we present a foam template-assisted (FTA) strategy for atmospheric pressure drying of cellulose nanofiber (CNF) aerogels. Building a robust CNF network is the key to resisting surface tension during water evaporation and achieving drying in ambient environments, which is achieved through cleverly designed ionic cross-linking with the help of FTA. Cellulose aerogel (CA) constructed using the FTA strategy exhibit lightweight (9 mg cm−3) and porous properties (porosity: > 99 %). The tannic-coated CA (TCA) was achieved by further polymerizing tannic acid on the CA surface, which has excellent photothermal conversion capability. Meanwhile, TCA achieved an impressive evaporation rate of 3.58 kg m-2h−1 and an energy efficiency of 97.2 % at 1sun radiation by virtue of its excellent energy confinement and water management capabilities. This strategy provides a promising solution for the low-cost construction of aerogels as well as for the realization of efficient solar-driven interfacial evaporators.

Superhydrophobic Cellulose Nanofiber Aerogels for Efficient Hemostasis with Minimal Blood Loss.

Reducing unnecessary blood loss in hemostasis is a major challenge for traditional hemostatic materials due to uncontrolled blood absorption. Tuning the hydrophilic and hydrophobic properties of hemostatic materials provides a road to reduce blood loss. Here, we developed a superhydrophobic aerogel that enabled remarkably reduced blood loss. The aerogel was fabricated with polydopamine-coated and fluoroalkyl chain-modified bacterial cellulose via a directional freeze-drying method. Primarily, the hydrophobic feature prevented blood from uncontrolled absorption by the material and overflowing laterally. Additionally, the aerogel had a dense network of channels that allowed it to absorb water from blood due to the capillary effect, and fluoroalkyl chains trapped the blood cells entering the channels to form a compact barrier via hydrophobic interaction at the bottom of the aerogel, causing quick fibrin generation and blood coagulation. The animal experiments reveal that the aerogel reduced the hemostatic time by 68% and blood loss by 87 wt % compared with QuikClot combat gauze. The study demonstrates the superiority of superhydrophobic aerogels for hemostasis and provides new insights into the development of hemostatic materials.

Effect of Activated Carbon on Cellulose Nanofiber Aerogels for Enhanced Solar Steam Generation

Effect of Activated Carbon on Cellulose Nanofiber Aerogels for Enhanced Solar Steam Generation

Optimizing sustainable construction: enhancing thermal insulation performance and energy savings with surface-modified cellulose nanofiber aerogels

Optimizing sustainable construction: enhancing thermal insulation performance and energy savings with surface-modified cellulose nanofiber aerogels

A mechanically robust and optically transparent nanofiber-aerogel-reinforcing polymeric nanocomposite for passive cooling window

The development of mechanically robust, visibly transparent and infrared spectrally selective films is pivotal for enhancing the thermal insulation efficiency of transparent building envelopes such as skylights and windows. Herein, an aligned nanofiber-aerogel-reinforcing all-polymeric nanocomposite is prepared by impregnating and curing methacrylate monomers within an aligned cellulose nanofiber aerogel. The deliberately structured cellulose aerogel with an aligned porous structure perpendicular to the film plane facilitates the formation of a robust nanofiber-matrix interface within the nanocomposite. This design enhances the mechanical strength and impact resistance reaching values of 274.5 MPa and 51.1 kJ m−2, respectively. Utilized as spectrally selective transparent window materials, these nanocomposites demonstrate exceptional infrared spectral selectivity, with a visible light transmittance of up to 78.2 %, near-infrared transmittance as low as 32.3 %, and mid-infrared emissivity as high as 91.0 %. They can be directly utilized as high-strength and impact-resistant spectrally selective cooling windows for effective indoor solar energy management, offering both indoor illumination and spontaneous cooling, leading to a reduction in indoor temperatures by 3.2 °C compared to conventional glass window materials.

Enhanced mechanical property and flame resistance of phosphorylated cellulose nanofiber based‐aerogel combined with boric acid

AbstractAs for cellulose‐based aerogels, a feature of inadequate mechanics and easy‐flammability seriously restricts their practical applications. To address this issue, herein a lightweight, mechanical elastic and flame‐retardant phosphorylated lignin‐based cellulose nanofiber (PLCNF‐B) aerogel with the aid of boric acid was successfully obtained by freeze‐drying method. Due to the uniform and tough network structure benefitting by strong hydrogen bond between phosphorylated fibers and boric acid, the resultant aerogel showed excellent mechanical performance, that is, high compressive strength of 8.9 kPa (strain: 50%) and outstanding cyclic reliability (remain 90% after 10 cycles). Meanwhile, PLCNF‐B aerogel possesses highly improved flame‐retardant property, that is, a high LOI value (up to 46%), significantly reduced peak heat release rate (11.2 W/g) and total heat release rate (0.47 kJ/g). Based on structural observation and analysis, the flame‐retardant behavior should be attributed to the formation of PxOy/amorphous boron oxide protective layer, which is derived from the phosphorus containing group of PLCNF and boric acid. The splendid overall performance of aerogel material offers a potential material tactic for design and development of advanced bio‐based aerogels for practical applications.

Flexible cellulose nanofiber aerogel with enhanced porous structure and its applications in copper(II) removal

In order to achieve an aerogel with both rigid pore structures and desired flexibility, stiff carboxyl-functionalized cellulose nanofiber (CNFs) were introduced into a flexible polyvinyl alcohol-polyethyleneimine (PVA-PEI) crosslinking network, with 4-formylphenylboronic acid (4FPBA) bridging within the PVA-PEI network to enable dynamic boroxine and imine bond formation. The strong covalent bonds and hydrogen connections between CNF and the crosslinking network enhanced the wet stability of the aerogel while also contributed to its thermal stability. Importantly, the harmonious coordination between the stiff CNF and the flexible polymer chains not only facilitated aerogel flexibility but also enhanced its increased specific surface area by improving pore structure. Moreover, the inclusion of CNF enhanced the adsorption capacity of the aerogel, rendering it effective for removing heavy metal ions. The specific surface area and adsorption capacity for copper ions of the aerogel increased significantly with a 3 wt% addition CNF suspension, reaching 19.74 m2 g−1 and 60.28 mg g−1, respectively. These values represent a remarkable increase of 590.21 % and 213.96 %, respectively, compared to the blank aerogel. The CNF-enhanced aerogel in this study, characterized by its well-defined pore structures, and desired flexibility, demonstrates versatile applicability across multiple domains, including environmental protection, thermal insulation, electrode fabrication, and beyond.

Ambient-dried, scalable and biodegradable cellulose nanofibers aerogel for oil-spill cleanup

Aerogels made of surface-modified cellulose nanofibers (CNF) have the potential to be a long-term solution for oil spill cleanup and industrial waste-water treatment, but their use is currently constrained by high preparation costs, lengthy processing times, and use of hazardous chemicals. In this study, a cost-effective and easily scalable cellulose nanofibers aerogel is developed using sugarcane bagasse as the cellulose source. The aqueous suspension of CNF and urea is freeze-thawed and then dried at ambient temperatures to produce CNF aerogels, avoiding the costly and time-consuming freeze-drying or supercritical drying methods. The role of urea in the aerogel structure is investigated using molecular dynamics. The aerogel exhibited an elastic modulus of 1345 KPa and a porosity of 96.9 %. To enhance the hydrophobicity of the surface of these aerogels, they are coated with the biodegradable polymer polycaprolactone (PCL). Further, two molecular weights (MW) PCL 10,000 and 80,000 are used to examine the impact of PCL MW on the performance and biodegradability of aerogel. Moreover, the efficacy of these green modifications is being compared to the conventional silane modifications. The 10,000 MW PCL-modified aerogel demonstrated a water-contact angle measuring 125.5°, an oil sorption capacity of 24 g/g, and exceptional recyclability even after undergoing 20 cycles. Further, after 15 days, the aerogel showed excellent biodegradability.

Harnessing the Flexibility of Lightweight Cellulose Nanofiber Composite Aerogels for Superior Thermal Insulation and Fire Protection.

Thermally insulating materials from renewable and readily available resources are in high demand for ecologically beneficial applications. Cellulose aerogels made from lignocellulosic waste have various advantages. However, they are fragile and breakable when bent or compressed. In addition, cellulose aerogels are flammable and weather-sensitive. Hence, to overcome these problems, this work included the preparation of polyurethane (PU)-based cellulose nanofiber (CNF) aerogels that had flexibility, flame retardancy, and thermal insulation. Methyl trimethoxysilane (MTMS) and water-soluble ammonium polyphosphate (APP) were added to improve the cross-linking, hydrophobicity, and flame-retardant properties of aerogels. The flexibility of chemically cross-linked CNF aerogels is enhanced through the incorporation of polyurethane via the wet coagulating process. The aerogels obtained during this study have exhibited low weight (density: 35.3-91.96 kg/m3) together with enhanced hydrophobic properties, flame retardancy, and decreased thermal conductivity (26.7-36.7 mW/m K at 25 °C). Additionally, the flame-retardant properties were comprehensively examined and the underlying mechanism was deduced. The aerogels prepared in this study are considered unique in the nanocellulose aerogel category due to their integrated structural and performance benefits. The invention is considered to substantially contribute to the large-scale manufacture and use of insulation in construction, automobiles, and aerospace.

Construction of metal-organic framework@cellulose nanofiber aerogel based on directional freezing for degradation of organic pollutants

Metal-organic frameworks (MOFs) can efficiently degrade organic pollutants through advanced oxidation processes (AOPs). However, the retrieval of MOFs from the solution poses a considerable challenge due to their powdery nature, thereby restricting their potential applications. Herein, a composite aerogel loaded with MOFs on cellulose nanofiber aerogel was prepared by directional freezing technology, which has orderly pore arrangement and excellent degradation performance. Directional freezing Co-MIL-53(Fe)@CNF has regular arranged pore structure and metal catalytic sites, efficiently activating peroxymonosulfate (PMS) and promoting the degradation of tetracycline hydrochloride (TC). The free radical quenching experiment and the electron paramagnetic resonance (EPR) experiment concurrently suggest that sulfate radicals and hydroxyl radicals, as prominent free radical species, play crucial roles in the degradation of TC. The pH level of the solution exhibits no discernible influence on the degradation process, indicating that the aerogel has good pH tolerance. This work provides a new strategy for developing an effective catalyst to activate PMS to eliminate antibiotics.

Polyaniline@cellulose nanofibers multifunctional composite material for supercapacitors, electromagnetic interference shielding and sensing

Recently, multifunctional materials have received widespread attention from researchers. Cellulose nanofibers (CNF) is one of biomass materials with abundant hydroxyl groups, which shows great potential in manufacturing multifunctional composite material. In this paper, a kind of polyaniline@CNF/polyvinyl alcohol-H2SO4 multifunctional composite material (PANI@CNF/PVA-H2SO4) was successfully designed by in-situ chemical polymerization of conductive polyaniline (PANI) onto CNF aerogel with high aspect ratio, and then coated with PVA-H2SO4 gel. The composite material has a specific capacitance of 502.2 F/g at a scan rate of 5 mV/s as supercapacitor electrode. Furthermore, when the composite was assembled into a symmetrical supercapacitor, it can still provide an energy density of 11.49 W·h/kg at a high power density of 413.55 W/kg. Besides, the as-obtained PANI@CNF/PVA-H2SO4 composite has an excellent electromagnetic shielding performance of 34.75 dB in X-band. In addition, due to the excellent flexibility of CNF and PVA, the PANI@CNF/PVA-H2SO4 composites can be further applied to stress sensors to detect pressure and human motion signals.

Highly Porous Yet Transparent Mechanically Flexible Aerogels Realizing Solar-Thermal Regulatory Cooling

HighlightsA lamellar-structured fluorinated cellulose nanofiber aerogel film is prepared by filtration-induced delaminated gelation and ambient drying.The aerogel film demonstrates exceptional mechanical flexibility and resistance to complex deformations.The aerogel film displays low thermal conductivity, high visible-light transmittance and superior selective infrared emissivity, rendering it high solar-thermal regulatory cooling performance.

Self-Assembled Aminated and TEMPO Cellulose Nanofibers (Am/TEMPO-CNF) Aerogel for Adsorptive Removal of Oxytetracycline and Chloramphenicol Antibiotics from Water.

Antibiotics are used for the well-being of human beings and other animals. Detectable levels of antibiotics can be found in pharmaceutical, municipal, and animal effluents. Therefore, the treatment of antibiotic contaminated water is of great concern. In this study, we fabricated a sustainable aminated/TEMPO cellulose nanofiber (Am/TEMPO-CNF) aerogel to remove oxytetracycline (OTC) and chloramphenicol (CAP) from synthetic wastewater. The prepared aerogel was characterized using different analytical techniques such as elemental analysis, FTIR, TGA, SEM-EDS, and N2 adsorption-desorption isotherms. The characterization techniques confirmed the presence and interaction of quaternary amine -[NR3]+ and -COOH groups on Am/TEMPO-CNF with OTC and CAP, which validates the successful modification of Am/TEMPO-CNF. The adsorption process of the pollutants was examined as a function of solution pH, concentrations, reaction time, and temperatures. The maximum adsorption capacity was 153.13 and 150.15 mg/g for OTC and CAP, respectively. The pseudo-second order (PSO-2) was well fitted to both OTC and CAP, confirming the removal is via chemisorption. Hydrogen bonding and electrostatic attraction have been postulated as key factors in facilitating OTC and CAP adsorption according to spectroscopic studies. Energetically, the adsorption was spontaneous and endothermic for both pollutants. In conclusion, the efficient removal rate and excellent reusability of Am/TEMPO-CNF indicate the strong potential of the adsorbent for antibiotics' removal.

Multifunctional amphibious superhydrophilic-oleophobic cellulose nanofiber aerogels for oil and water purification

Aerogels are of a popular choice for oil-water separation and water purification due to their attractive properties, such as lightweight, large surface area, and high porosity. Developing robust aerogels with multifunctional characteristics is highly desirable but remains challenging nowadays. Herein, we develop a facile one-pot condensation strategy for the fabrication of superhydrophilic-oleophobic (SHI-OP) composite aerogels using cellulose nanofibers (CNF), 3-glycidy-loxypropyl trimethoxysilane (GPTMS), polyethyleneimine (PEI) and fluorine-contained compound (FS-60). The resulted aerogels exhibit a directional lamellar structure with interconnected macropores, super-lightweight with high porosity of 98.30 % and low density of 0.0256 g·cm−3. Also, the aerogels are mechanically durable against repeated compression. Meanwhile, the amphibious SHI-OP feature of the composite aerogels in both air and water states enables them to not only absorb trace amount of water from contaminated oils, but also separate oil-water mixtures with separation efficiency of over 99 % and high permeation flux of over 9060 L/m2·h. Moreover, the aerogels also show excellent dye adsorption capability and reusability toward anionic dyes with a maximum adsorption capacity of 1245.68 mg/g. Such robust and multifunctional aerogels with special surface wettability provide good opportunity for liquid purification and dye-containing wastewater treatment.

Bioadsorbent nanocellulose aerogel efficiency impregnated with spent coffee grounds

Due to growing environmental concerns for better waste management, this study proposes developing a composite aerogel using cellulose nanofibers (CNF) and spent coffee grounds (SCG) through an eco-friendly method for efficient methylene blue (MB) adsorption. Adding SCG to the CNF aerogel altered the physical properties: it increases the volume (4.14 cm3 to 5.25 cm3) and density (0.018 to 0.022 g/cm3) but decrease the water adsorption capacity (2064 % to 1635 %). FTIR spectrum showed distinct functional groups in both all aerogels, showing hydroxyl, glyosidic bonds, and aromatic compounds. Additionally, SCG improved thermal stability of the aerogels. In term of adsorption efficacy, CNF-SCG40% aerogel as exceptionally well. According to Langmuir isotherm models, the adsorption of MB happened in a monolayer, with CNF-SCG40% showing a maximum adsorption capacity of 113.64 mg/g, surpassing CNF aerogel (58.82 mg/g). The study identified that the pseudo-second-order model effectively depicted the adsorption process, indicating a chemical-like interaction. This investigation successfully produced a single-use composite aerogel composed of CNF and SCG using an eco-friendly approach, efficiently adsorbing MB. By utilizing cost-effective materials and eco-friendly methods, this approach offers a sustainable solution for waste management, contributes to an eco-friendly industrial environment, and reduces production expenses and management costs.

SCG-Based CNF Aerogels with Oriented and Aligned Porous Structure for Solar Interfacial Desalination.

Spent coffee grounds are recognized as a green and sustainable resource of cellulose nanofiber (CNF), which can further form aerogels with rGO for solar-driven interfacial desalination via directional freezing technology. The vertically arranged channels provide better photothermal conversion performance and salt tolerance of rGO/CNF aerogels. Their max evaporation rate can reach to 2.729 kg·m-2·h-1 under natural sunlight. In terms of long-term application (10 days), the aerogels exhibit a stable evaporation property in outdoor environments. The optimum daily average water yield is 15.00 L·m-2, which can fulfill the daily water requirement of six people.

Carbon sphere@layered double hydroxides filled cellulose nanofibers aerogel for Cr(VI) adsorption from aqueous solution

ABSTRACT Carbon sphere@layered double hydroxides filled cellulose nanofibers (ACS@LDHs/CNF) aerogel was successfully synthesized. The removal rate of Cr(VI) using ACS@LDHs/CNFs aerogel at a solid-liquid ratio of 1 g/L was 89.4%, which was higher compared to the removal rate of 65.2% using LDHs alone. The adsorption capacity of ACS@LDHs/CNFs for Cr(VI) was determined to be 44.9 mg/g. The adsorption kinetics followed the pseudo-second-order kinetic equation, and the isotherm data showed good agreement with the Langmuir model. The adsorption mechanism of Cr(VI) onto ACS@LDHs/CNFs aerogel was also investigated. Additionally, the ACS@LDHs/CNFs aerogel demonstrated consistent high adsorption efficiency over 4 consecutive cycles of adsorption-regeneration.

Iron Oxide Nanoparticle-Loaded Magnetic Cellulose Nanofiber Aerogel with Self-Controlled Release Property for Green Active Food Packaging

Iron Oxide Nanoparticle-Loaded Magnetic Cellulose Nanofiber Aerogel with Self-Controlled Release Property for Green Active Food Packaging