This
work demonstrates the confinement of porous metal–organic
framework (HKUST-1) on the surface and walls of track-etched nanochannel
in polyethylene terephthalate (np-PET) membrane using a liquid-phase
epitaxy (LPE) technique. The composite membrane (HKUST-1/np-PET) exhibits
defect-free MOF growth continuity, strong attachment of MOF to the
support, and a high degree of flexibility. The high flexibility and
the strong confinement of the MOF in composite membrane results from
(i) the flexible np-PET support, (ii) coordination attachment between
HKUST-1 and the support, and (iii) the growth of HKUST-1 crystal in
nanoconfined geometries. The MOF has a preferred growth orientation
with a window size of 3.5 Å, resulting in a clear cut-off of
CO2 from natural gas and olefins. The experimental results
and DFT calculations show that the restricted diffusion of gases only
takes place through the nanoporous MOF confined in the np-PET substrate.
This research thereby provides a new perspective to grow other porous
MOFs in artificially prepared nanochannels for the realization of
continuous, flexible, and defect-free membranes for various applications.
Herein, we report a rapid and facile synthetic methodology for robust, nanostructured films of cobalt oxide over metal evaporated gold layer of 50 nm, directly onto plain glass substrates via aerosol assisted chemical vapor deposition (AACVD) approach. The films thus prepared are characterized by XRD, SEM, and EDX spectroscopy as a function of deposition time (i.e., 5 min -20 min). It is remarkably shown that the film growth rate is 0.8 nmSec −1 using this AACVD method and a commercially available precursor, which is ∼10 times higher as compared to the electrochemical synthetic routes. As a result, 250 nm thick cobalt oxide films are generated only in 5 minutes of deposition time. The water oxidation reaction for this film started at ∼0.6 V vs Ag/AgCl with current density of 10 mA cm −2 is achieved at ∼0.75 V that corresponds to an overpotential of 484 mV. This current density is further increased to 60 mA cm −2 at ∼1.5 V (vs Ag/AgCl). Electrochemically active surface area (ECSA) calculations are also performed which indicated that the synergy between Au-film acting as electron sink and the cobalt oxide film acting as catalytic layer are more pronounced than the surface area effects.
This study examines the piezoresistive behavior of MWCNT/polymer composites fabricated by the digital light processing (DLP) technique. A photocurable nanocomposite resin feedstock possessing low viscosity with excellent printability and high conductivity was developed for DLP 3D printing of bulk and cellular geometries. By optimizing the resin composition and synthesis route, electrical percolation was achieved at an ultra-low MWCNT loading of 0.01 phr (parts per hundred resin), providing a conductivity of 3.5 × 10−5 S m−1, which is significantly higher than the values reported in the extant works for similar nanocomposites. Reducing the MWCNT content also enhanced the piezoresistivity of the nanocomposite due to longer inter-MWCNT distances in the percolating conductive network. Under quasi-static tensile loading, the nanocomposite with 0.01 phr MWCNT loading showed gauge factors of 2.40 and 4.78, corresponding to the elastic and inelastic regime, respectively. Quasi-static cyclic tensile tests with constant strain amplitudes (within elastic regime) revealed that the response of the nanocomposite was affected by viscoelastic deformation, which caused significant changes in the material’s strain sensing performance between consecutive load cycles. Finally, the developed resin was used to realize a self-sensing gyroid lattice structure, and its strain and damage sensing capabilities were demonstrated.
This study investigates the mechanical and piezoresistive self‐sensing performance of additive manufacturing‐enabled 2D nanocomposite lattices under monotonic and cyclic tensile loading. Lattice structures comprising hexagonal, chiral, triangular, and reentrant unit cell topologies are realized via digital light processing using an acrylic photocurable resin filled with carbon nanotubes (CNTs). The results reveal that the piezoresistive sensitivity of reentrant and triangular lattices is nearly insensitive to changes in relative density. In contrast, the gauge factors of the hexagonal and chiral lattices rise by 300% and 500%, respectively, with an increase in relative density from 20 to 40%, which can be ascribed to their bend‐dominated behavior, causing an increase in surface strains in the lattice struts with increasing relative density for an imposed macroscopic strain. The measured stress versus strain responses compare well with nonlinear finite element results. Under strain‐controlled cyclic loading, the electrical resistance of the 2D lattices is found to decline over time due to reorientation of the CNTs in the surrounding viscoelastic polymer matrix. The findings provide valuable insights into the interrelations between sensing performance, cell architecture, and relative density of the lattices, and offer guidelines for the design of architected strain sensors and self‐sensing lightweight structures.
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