Search

Chemically modified graphene is commonly used as a desensitizer and combustion catalyst for energetic composites. However, the interaction between polar functional groups on chemically modified graphene and energetic ionic materials has not been explored systematically. Herein, we use graphene oxide (GO) with different oxidation degrees and dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) as experimental systems to investigate the effect of oxygen-containing functional groups of GO on the pyrolysis mechanism of energetic ionic materials. The experimental results show that the thermal decomposition of TKX-50 is affected by different oxidation degrees of GO, among which the highly oxidized GO (HGO) has the greatest effect. The thermal decomposition temperature of GO/TKX-50 composites decrease with the increase of oxygen-containing group content. The decomposition products of GO/TKX-50 composites are consistent with those of TKX-50, but the content of gas products changed. We argue that the interaction between the oxygen-containing groups of GO and TKX-50 controls the pyrolysis mechanism by promoting the transfer of protons in hydroxyl, (NH3OH)+, and (NH4)+, at least in the context of oxygen-containing functional groups. This work provides a route to manipulate the thermal decomposition temperature and gaseous product of the final compound through functional group content, which is helpful to study the polar functional group of chemically modified graphene for the modification of energetic materials. [ABSTRACT FROM AUTHOR]

Highlights: Large-area production of self-standing graphene nanofilm (~ 20 cm) through a clean 'substrate replacement' strategy. Realizing highly crystalline graphene nanofilms without micro-gasbags by introducing polymers. The graphene nanofilms demonstrate a solid light–matter interaction (photoelectric conversion in the mid-infrared and electromagnetic interference (EMI) shielding in X-band) with performance beyond state-of-the-art graphene/silicon diodes and EMI materials. Bulk graphene nanofilms feature fast electronic and phonon transport in combination with strong light–matter interaction and thus have great potential for versatile applications, spanning from photonic, electronic, and optoelectronic devices to charge-stripping and electromagnetic shielding, etc. However, large-area flexible close-stacked graphene nanofilms with a wide thickness range have yet to be reported. Here, we report a polyacrylonitrile-assisted 'substrate replacement' strategy to fabricate large-area free-standing graphene oxide/polyacrylonitrile nanofilms (lateral size ~ 20 cm). Linear polyacrylonitrile chains-derived nanochannels promote the escape of gases and enable macro-assembled graphene nanofilms (nMAGs) of 50–600 nm thickness following heat treatment at 3,000 °C. The uniform nMAGs exhibit 802–1,540 cm2 V−1 s−1 carrier mobility, 4.3–4.7 ps carrier lifetime, and > 1,581 W m−1 K−1 thermal conductivity (nMAG-assembled 10 µm-thick films, mMAGs). nMAGs are highly flexible and show no structure damage even after 1.0 × 105 cycles of folding–unfolding. Furthermore, nMAGs broaden the detection region of graphene/silicon heterojunction from near-infrared to mid-infrared and demonstrate higher absolute electromagnetic interference (EMI) shielding effectiveness than state-of-the-art EMI materials of the same thickness. These results are expected to lead to the broad applications of such bulk nanofilms, especially as micro/nanoelectronic and optoelectronic platforms. [ABSTRACT FROM AUTHOR]

The anti‐migration ethylene propylene diene terpolymer (EPDM) inhibitor coating was prepared by using EPDM as a composite matrix and silicon‐functionalized graphene oxide (GO‐SiO2) as modifiers to prevent the migration of energetic plasticizers in propellants. The anti‐migration performance at different temperatures was analyzed by investigating the diffusion of dioctyl sebacate (DOS) using thermal analysis and immersion tests. After adding 1.0 wt% GO‐SiO2, the overall performance of the inhibitor coating was the best, and the concentration of DOS that migrated into the inhibitor coating at 30°C was reduced from 45.1% to 38.8% (13.9% decrease). The results confirmed that the introduction of GO‐SiO2 prevented the migration of dioctyl sebacate to the EPDM inhibitor coating. The scanning electron microscopy results showed that GO‐SiO2 was well‐dispersed in the inhibitor coating, and the tensile strength increased from 1.80 to 2.11 MPa. Migration kinetics analysis showed that the anti‐migration performance was closely related to the crosslink density. [ABSTRACT FROM AUTHOR]

In this paper, the ethylene propylene diene monomer (EPDM) was used as a composite matrix and octadecylamine‐functionalized graphene oxide (GA) was applied as insulation nanofiller to prevent plasticizer migration. To study the anti‐migration behavior of EPDM under plasticizer environment and different temperatures, we investigated the diffusion of dioctyl phthalate (DOP) in EPDM and its composites. The migration kinetics of DOP into EPDM composites with respect to filler and temperature were observed by the immersion absorption method. The process is dynamic and conforms to Fick's law. The composite show a 90% increase in tensile strength and 151% improvement in elongation at break by the addition of 5 phr filler of GA. Meanwhile, the EPDM/GA composite show an obviously improved anti‐migration performance, compared to pure EPDM at different temperatures, the composite show a 22.68%, 17.35%, 14.95%, 7.63% increase. Well layer‐structure of graphene offers a chance to improve the anti‐migration performance of insulation. [ABSTRACT FROM AUTHOR]

Abstract: Graphene aerogel microlattices (GAMs) hold great prospects for many multifunctional applications due to their low density, high porosity, designed lattice structures, good elasticity, and tunable electrical conductivity. Previous 3D printing approaches to fabricate GAMs require either high content of additives or complex processes, limiting their wide applications. Here, a facile ion‐induced gelation method is demonstrated to directly print GAMs from graphene oxide (GO) based ink. With trace addition of Ca2+ ions as gelators, aqueous GO sol converts to printable gel ink. Self‐standing 3D structures with programmable microlattices are directly printed just in air at room temperature. The rich hierarchical pores and high electrical conductivity of GAMs bring admirable capacitive performance for supercapacitors. The gravimetric capacitance (Cs) of GAMs is 213 F g−1 at 0.5 A g−1 and 183 F g−1 at 100 A g−1, and retains over 90% after 50 000 cycles. The facile, direct 3D printing of neat graphene oxide can promote wide applications of GAMs from energy storage to tissue engineering scaffolds. [ABSTRACT FROM AUTHOR]

Meta-periodicity beyond intrinsic atomic and molecular order, such as metacrystalline and quasicrystalline lattices, exists in solids, but is usually elusive in lyotropic liquid crystals for its energetic instability. The stable meta-periodicity in lyotropic liquid crystals in the absence of external stimuli remains unexplored, and how to achieve it keeps a great challenge. Here we create lyotropic liquid crystals with stable meta-periodicity in a free state, coined as liquid metacrystals, in colloidal systems by an invented shearing microlithography. The meta-periodicity is dynamically stabilized by the giant molecular size and strong excluded volume repulsion. Liquid metacrystals are designed to completely cover a library of symmetries, including five Bravais and six quasicrystalline lattices. Liquid metacrystal promises an extended form of liquid crystals with rich meta-periodicity and the shearing microlithography emerges as a facile technology to fabricate liquid meta-structures and metamaterials, enabling the digital design of structures and functionalities of liquid crystalline materials. Stable periodic structures can be difficult to obtain in a liquid crystal compared to a solid due to the energetic instability of the former. Here the authors present a technique to fabricate quasicrystalline structures of graphene oxide liquid crystals which have high stability. [ABSTRACT FROM AUTHOR]

Stimuli-responsive fusion and fission are widely observed in both bio-organizations and artificial molecular assemblies. However, the design of a system with structure and property persistence during repeated fusion and fission remains challenging. We show reversible fusion and fission of wet-spun graphene oxide (GO) fibers, in which a number of macroscopic fibers can fuse into a thicker one and can also separate into original individual fibers under stimulation of solvents. The dynamic geometrical deformation of GO fiber shells, caused by solvent evaporation and infiltration, is the key to the reversible fusion-fission cycles. This principle is extended to implement flexible transitions between complex fiber assemblies and the inclusion or expulsion of guest compounds. [ABSTRACT FROM AUTHOR]

Processing solvated graphene by ink printing technique holds exciting prospective in fabricating macroscopic carbonaceous materials with designed structures and outstanding properties. Direct ink writing has been utilized for highly porous graphene aerogels for multifunctional uses. However, densified graphene solid materials have kept unreached by 3D printing for the conflict between high concentration and good homogeneousness of printing ink. Here, we have fabricated high density compact graphene microlattices (CGM) with ordered structure via liquid crystalline (LC) direct ink writing. Concentrated but homogeneous graphene oxide/glycerol inks were prepared, reaching a solid containing up to ∼6 wt% and possessing LC nature. The flow unified LC order of inks renders highly ordered micro-structure of CGM, outstanding compressive strength (62.7 MPa at 90% strain) and high electrical conductivity of 2073 S m−1. Our CGM also exhibit an impressive elasticity up to 15–18% strain. Our facile methodology has introduced a graphene solid architecture material with high mechanical properties and multi functionalities, which should become a useful engineered carbon scaffolds with designed multiscale structures, mechanical and functional properties. Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] • FeNi or FeCo@N-doped graphene layer core–shell heterojunctions/N-doped carbon nanorods/rGO composites were synthesized. • The filler loading and rGo could effectively adjust the permittivity. • The strong absorption was achieved of −52.61 dB and −59.42 dB. • The effective absorption bandwidths were up to 4.64 GHz and 5.28 GHz. Rational construction of heterogeneous interfaces is an effective strategy to explore high-performance electromagnetic waves (EMWs) absorption materials. Herein, we adopt a facile solvothermal and pyrolysis process to fabricate the multicomponent and multidimensional composites containing the bimetallic FeNi or FeCo@N-doped graphene layer core–shell heterojunctions/N-doped carbon nanorods/reduced graphene oxide (FeNi@NC/NCR/rGO or FeCo@NC/NCR/rGO) derived from NH 2 -bimetallic (FeNi or FeCo)-metal organic frameworks (MOFs)/GO precursors. The excellent EMWs absorption performances are effectively achieved and regulated via the content of rGO and the filler loading. Compared with the case without rGO, the FeNi@NC/NCR/rGO composite (25 wt% filler loading) displays a strong reflection loss (RL) of −52.61 dB at 14.44 GHz with a thin thickness of 1.65 mm, and effective absorption bandwidth (EAB) is 4.64 GHz. And the FeCo@NC/NCR/rGO composite (20 wt% filler loading) displays a strong RL of −59.42 dB at 17.8 GHz with a thinner thickness of 1.42 mm, and EAB is 5.28 GHz at 1.66 mm. Their excellent absorption properties result from the synergistic effect between the increased dielectric loss (interfacial polarization, dipole polarization and conduction loss), impedance matching and attenuation constant. These results provide a pathway to prepare the multicomponent and multidimensional composites with superior EMWs absorption. [ABSTRACT FROM AUTHOR]