RESUMO
A metal-organic framework (MOF) based on a conjugated organic ligand and a transition-metal ion was designed and used to construct a novel multiwalled carbon nanotube (MWNT)/MOF interphase via hierarchical assembly on the carbon fiber (CF) surface and was compared to various interphases established by MWNT and MOF. An intertwined MWNT and MOF "jujube core" was randomly dispersed on MWNT@CF and MOF@CF surfaces, while interpenetrating structures with the MWNT network and MOF jujube core were simultaneously observed on MWNT/MOF@CF due to coordination bonds and π-π conjugation effects, which were derived from the MWNT template with carboxyl groups and sp2-hybridized domains as well as the secondary growth of MOF to promote self-assembly and the connection of MOF. The transverse fiber bundle test (TFBT) strength and interfacial shear strength (IFSS) of the MWNT/MOF@CF composite were 36.9, 6.1, and 20.8%, 16.3% higher than those of MWNT@CF and MOF@CF composites, which were attributed to the smoothed modulus transition of the stiffening interphase formed by the MWNT/MOF hybrid structure as "armor" to effectively buffer the stress transfer between a carbon fiber and the resin matrix. Compared to MWNT@CF and MOF@CF composites, MWNT/MOF@CF composites had the highest EMI shielding effectiveness, which was attributed to the combined effects of multiple reflections, conductive loss, and interface polarization from the interpenetrating MWNT/MOF hybrid structures, which realized the integration of the structure and function of the carbon fiber composites.
RESUMO
Accurate dosing for various liquids, especially for highly viscous liquids, is fundamental in wide-ranging from molecular crosslinking to material processing. Despite droppers or pipettes being widely used as pipetting devices, they are powerless for quantificationally splitting and dosing highly viscous liquids (>100 mPa s) like polymer liquids due to the intertwined macromolecular chains and strong cohesion energy. Here, a highly transparent photopyroelectric slippery (PS) platform is provided to achieve noncontact self-splitting for liquids with viscosity as high as 15 000 mPa s, just with the assistance of sunlight and a cooling source to provide a local temperature difference (ΔT). Moreover, to guarantee the accuracy for pipetting liquids (>80%), the ultrathin MXene film (within a thickness of 20 nm) is self-assembled as the photo-thermal layers, overcoming the trade-off between transparency and photothermal property. Compared with traditional pipetting strategies (≈1.3% accuracy for pipetting polymer liquids), this accurate microfluidic chip shows great potential in adhesive systems (bonding strength, twice than using the droppers or pipettes).
RESUMO
Cobalt tetraoxide (Co3O4) is regarded as a promising anode material for Li-ion batteries owing to its high theoretical capacity (890 mAh g-1), simple preparation, and controllable morphology. Nanoengineering has been proven to be an effective method for producing high-performance electrode materials. However, systematic research on the influence of material dimensionality on battery performance is lacking. Herein, we prepared Co3O4 with various dimensionalities (one-dimensional (1D) Co3O4 nanorod (NR), two-dimensional (2D) Co3O4 nanosheet (NS), three-dimensional (3D) Co3O4 nanocluster (NC), and 3D Co3O4 nanoflower (NF)) using a simple solvothermal heat treatment method, and their morphologies were controlled by varying the precipitator type and solvent composition. The 1D Co3O4 NR and 3D samples (3D Co3O4 NC and 3D Co3O4 NF) exhibited poor cyclic and rate performances, respectively, while the 2D Co3O4 NS exhibited the best electrochemical performance. The mechanism analysis revealed that the cyclic stability and rate performance of the Co3O4 nanostructures are closely related to their intrinsic stability and interfacial contact performance, respectively, and the 2D thin-sheet structure can achieve an optimal balance between the two, resulting in the best performance. This work presents a comprehensive study on the effect of dimensionality on the electrochemical performance of Co3O4 anodes, providing a new concept for the nanostructure design of conversion-type materials.
RESUMO
A rigid-and-flexible interphase was established by a starlike copolymer (Pc-PGMA/Pc) consisting of one tetraaminophthalocyanine (TAPc) core with four TAPc-difunctionalized poly(glycidyl methacrylate) (PGMA) arms through the surface modification of carbon fibers (CFs) and compared with various interphases constructed by TAPc and TAPc-connected PGMA (Pc-PGMA). The increase in the content of N-CâO showed that PGMA/Pc branches were successfully attached onto the CF-(Pc-PGMA/Pc) surface, exhibiting concavo-convex microstructures with the highest roughness. Through adhesive force spectroscopy by atomic force microscopy (AFM) with peak force quantitative nanomechanical mapping (PF-QNM) mode and visualization of the relative distribution of TAPc/PGMA via a Raman spectrometer, a rigid interphase with highly cross-linked TAPc and a flexible layer from PGMA arms as the soft segment were separately detected in CF-TAPc/EP and CF-(Pc-PGMA)/EP composites. The rigid-and-flexible interphase in the CF-(Pc-PGMA/Pc)/EP composite provided excellent stress-transfer capability by the rigid inner modulus intermediate layer and energy absorption efficiency from the flexible outer layer, which contributed to 64.6 and 61.8% increment of transverse fiber bundle test (TFBT) strength, and 33.8 and 40.6% enhancement in interfacial shear strength (IFSS) in comparison with those of CF-TAPc/EP and CF-(Pc-PGMA)/EP composites. Accordingly, schematic models of the interphase reinforcing mechanism were proposed. The interfacial failures in CF-TAPc/EP and CF-(Pc-PGMA)/EP composites were derived from the rigid interphase without effective relaxation of interfacial stress and soft interphase with excessive fiber-matrix interface slippage, respectively. The cohesive failure in the CF-(Pc-PGMA/Pc)/EP composite was attributed to the crack deflection through the balance of the modulus and deformability from the twin-stage gradient intermediate layer.