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As technology advances toward ongoing circuit miniaturization and device size reduction followed by improved power density, heat dissipation is becoming a key challenge for electronic equipment. Heat accumulation can be prevented if the heat from electrical equipment is efficiently exported, ensuring a device's lifespan and dependability and preventing otherwise possible mishaps or even explosions. Hence, thermal management applications, which include altering the role of aerogels from thermally insulative to thermally conductive, have recently been a hot topic for 3D-aerogel-based thermal interface materials. To completely comprehend three-dimensional (3D) networks, we categorized and comparatively analyzed aerogels based on carbon nanomaterials, namely fibers, nanotubes, graphene, and graphene oxide, which have capabilities that may be fused with boron nitride and impregnated for better thermal performance and mechanical stability by polymers, including epoxy, cellulose, and polydimethylsiloxane (PDMS). An alternative route is presented in the comparative analysis by carbonized cellulose. As a result, the development of structurally robust and stiff thermally conductive aerogels for electronic packaging has been predicted to increase polymer thermal management capabilities. The latest trends include the self-organization of an anisotropic structure on several hierarchical levels within a 3D framework. In this study, we highlight and analyze the recent advances in 3D-structured thermally conductive aerogels, their potential impact on the next generation of electronic components based on advanced nanocomposites, and their future prospects.

In this study, three-dimensional (3D) polyvinyl alcohol (PVA)/aligned boron nitride (BN) aerogel framework nanocomposites with high performance were fabricated by a facile strategy. The boron nitride powder was initially hydrolyzed and dispersed with a chemically crosslinked plasticizer, diethyl glycol (DEG), in the PVA polymer system. The boron nitride and DEG/PVA suspensions were then mixed well with different stoichiometric ratios to attain BN/PVA nanocomposites. Scanning electron microscopy revealed that BN platelets were well dispersed and successfully aligned/oriented in one direction in the PVA matrix by using a vacuum-assisted filtration technique. The formed BN/PVA aerogel cake composite showed excellent in-plane and out-of-plane thermal conductivities of 0.76 W/mK and 0.61 W/mK with a ratio of BN/PVA of (2:1) in comparison with 0.15 W/mK for the pure PVA matrix. These high thermal conductivities of BN aerogel could be attributed to the unidirectional orientation of boron nitride nanoplatelets with the post-two days vacuum drying of the specimens at elevated temperatures. This aerogel composite is unique of its kind and displayed such high thermal conductivity of the BN/PVA framework without impregnation by any external polymer. Moreover, the composites also presented good wettability results with water and displayed high electrical resistivity of ~10 14 Ω cm. These nanocomposites thus, with such exceptional characteristics, have a wide range of potential uses in packaging and electronics for thermal management applications.

Biopolymer/silica nanocomposite aerogels are highly attractive as thermally insulating materials for prevailing energy-saving engineering but are usually plagued by their lack of mechanical strength and environmental stability. Lignin is an appealing plant phenolic biopolymer due to its natural abundance, high stiffness, water repellency, and thermostability. However, integrating lignin and silica into high-performance 3D hybrid aerogels remains a substantial challenge due to the unstable co-sol process. In diatoms, the silicic acid stabilization prior to the condensation reaction is enhanced by the intervention of biomolecules in noncovalent interactions. Inspired by this mechanism, we herein rationally design an ultrastrong silica-mineralized lignin nanocomposite aerogel (LigSi) with an adjustable multilevel micro/nanostructure and arbitrary machinability through an unusual water-induced self-assembly and in situ mineralization based on ethylene glycol-stabilized lignin/siloxane colloid. The optimized LigSi exhibits an ultrahigh stiffness (a specific modulus of ∼376.3 kN m kg -1 ) and can support over 5000 times its own weight without obvious deformation. Moreover, the aerogel demonstrates a combination of outstanding properties, including superior and humidity-tolerant thermal insulation (maintained at ∼0.04 W m -1 K -1 under a relative humidity of 33-94%), excellent fire resistance withstanding an ∼1200 °C flame without disintegration, low near-infrared absorption (∼9%), and intrinsic self-cleaning/superhydrophobic performance (158° WCA). These advanced properties make it an ideal thermally insulating material for diversified applications in harsh environments. As a proof of concept, a dual-mode LigSi thermal device was designed to demonstrate the application prospect of combining passive heat-trapping and active heating in the building.

Bacterial cellulose (BC) aerogel owing to its porous and 3D structure, poses a suitable matrix for embedding nanomaterials and polymers. Herein, BC composites comprising nano-clay/polyaniline (PANI) were synthesized via a two-step procedure. Clay nanoplatelets were dispersed in the BC membrane to form a nanofibrillated template for aniline in-situ polymerization leading to formation of a double interconnected network of electrically conductive path within the aerogel. Deposition of PANI particles on BC/clay nanocomposite was confirmed by FTIR, XRD, FESEM, and EDX techniques. The surface electrical conductivity of 0.49 S/cm was obtained for the composite aerogel comprising 5 wt% nano-clay which is 16 folds higher than that of the sample without nano-clay. Thermal stability and storage modulus of the aerogels was improved by inclusion of PANI and nano-clay. Synergistic effect of clay and polyaniline on biocompatibility and cell adhesion was obtained with no mutagenic or carcinogenic effects. The developed electrically conductive composite aerogels can be utilized as suitable scaffolds for tissue engineering applications demanding a good balance of flexibility, dimensional and thermal stability and biocompatibility., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this work, the structure-property relationship was evaluated in the synthesis of bacterial cellulose (BC)/polyaniline (PANI) nanocomposite aerogels in terms of both experimental and density functional theory (DFT) simulation. The molarity of HCl solution (0.01 and 0.5 M) and the presence/absence of cetyltrimethylammonium bromide (CTAB) were the main parameters of synthesis conditions. DFT simulation showed that the formation of hydrogen bonds governed interaction between BC and PANI, and PANI had more tendency to BC than that of CTAB at 0.5 M. It was confirmed by the formation of shorter hydrogen bonds between BC and protonated PANI at 0.5 M. Regarding this fact, prepared samples at 0.5 M of HCl solution and the presence of CTAB experienced higher storage modulus and electrical conductivity by 2000 Pa and 4 order of magnitude than those of lower molarity (0.01 M). These findings were in accordance with simulation outcomes., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Herein, polyaniline (PANI) with tuning morphology was in-situ synthesized within bacterial cellulose (BC)/silver nanoparticles hydrogels (AgNPs) that were prepared by green hydrothermal reduction method in different molarity of 0.01 and 0.25 of HCl solution along with the presence of polyethylene glycol (PEG). The synthesis of PANI in the presence of PEG in 0.01 M HCl led to the formation of rose-like morphology within nanocomposite aerogels with a size of 1.5-5.2 μm. All aerogels had the porosity and shrinkage of higher than 80% and lower than 10%, respectively. Rheology results showed a higher value of storage modulus (G') than that of loss modulus (G″) for all samples over the whole frequency regime. It confirmed by the loss factor (tan δ) value of less than 1 for all hydrogel samples. The synthesis of PANI within BC/Ag in 0.25 M of HCl solution resulted in a substantial rise of G' to nearly 1.5 × 10 4  Pa that was one order of magnitude higher than that of other hydrogels. However, the synthesis condition of PANI did not influence the antibacterial activity. In spite of unfavorable cell attachment onto nanocomposite aerogels, the cell proliferation increased steadily over the whole period of incubation., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)