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This paper introduces a pioneering approach that combines ex situ synthesis with advanced manufacturing to develop ZIF-67-PA12 Nylon composites with mixed-matrix membranes (MMMs), with the goal of enhancing hydrogen storage systems. One method involves producing MOF-PA12 composite powders through an in situ process, which is then commonly used as a base powder for powder bed fusion (PBF) to fabricate various structures. However, developing the in situ MOF-PA12 matrix presents challenges, including limited spreadability and processability at higher MOF contents, as well as reduced porosity due to pore blockage by polymers, ultimately diminishing hydrogen storage capacity. To overcome these issues, PBF is employed to form PA12 powder into films, followed by the ex situ direct synthesis of ZIF-67 onto these substrates at loadings exceeding those typically used in conventional MMM composites. In this study, ZIF-67 mass loadings ranging from 2 to 30 wt.% were synthesized on both PA12 powder and printed film substrates, with loadings on printed PA12 films extended up to 60 wt.%. ZIF-67-PA12-60(f) demonstrated a hydrogen capacity of 0.56 wt.% and achieved 1.53 wt.% for ZIF-67-PA12-30(p); in comparison, PA12 exhibited a capacity of 0.38 wt.%. This was undertaken to explore a range of ZIF-67 Metal–organic frameworks (MOFs) to assess their impact on the properties of the composite, particularly for hydrogen storage applications. Our results demonstrate that ex situ-synthesized ZIF-67-PA12 composite MMMs, which can be used as a final product for direct application and do not require the use of in situ pre-synthesized powder for the PBF process, not only retain significant hydrogen storage capacities, but also offer advantages in terms of repeatability, cost-efficiency, and ease of production. These findings highlight the potential of this innovative composite material as a practical and efficient solution for hydrogen storage, paving the way for advancements in energy storage technologies. [ABSTRACT FROM AUTHOR]

In this study, a reactive adsorbent filler was integrated into a polymeric matrix as a novel reactive protective barrier without undermining its mechanical, thermal, and chemical properties. For this purpose, newly synthesized TiO2/MCM/polydimethylsiloxane (PDMS) composites were prepared, and their various properties were thoroughly studied. The filler, TiO2/MCM, is based on a (45 wt%) TiO2 nanoparticle catalyst inside the pores of ordered mesoporous silica, MCM-41, which combines a high adsorption capacity and catalytic capability. This study shows that the incorporation of TiO2/MCM significantly enhances the composite's Young's modulus in terms of tensile strength, as an optimal measurement of 1.6 MPa was obtained, compared with that of 0.8 MPa of pristine PDMS. The composites also showed a higher thermal stability, a reduction in the coefficient of thermal expansion (from 290 to 110 ppm/°C), a 25% reduction in the change in the normalized specific heat capacity, and an increase in the thermal degradation temperatures. The chemical stability in organic environments was improved, as toluene swelling decreased by 40% and the contact angle increased by ~15°. The enhanced properties of the novel synthesized TiO2/MCM/PDMS composite can be used in various applications where a high adsorption capacity and catalytic/photocatalytic activity are required, such as in protective equipment, microfluidic applications, and chemical sensor devices. [ABSTRACT FROM AUTHOR]

In this article, the limits of thin-film deposition on very rough topographies are demonstrated by depositing alumina on vertically aligned carbon nanotubes (VACNTs). Vapor deposition techniques are the enabling platforms of the thin-film industry, offering high material versatility and good coverage ability on relatively flat surfaces, leading to frequent use in a large array of applications, especially nanoscale electronic devices such as sensors and electrodes. However, when surface topography exhibits high roughness, even depositions that are not limited to line-of-sight show only partial coverage, significantly hindering performances. Our manufacturing process of VACNT/Al2O3 nanocomposites has three vaporous steps: CNT growth by chemical vapor deposition (CVD), functionalization via controlled thermal oxidation, and atomic layer deposition (ALD) of alumina. The same limited accessibility hinders each of these three steps. Morphological analyses show different CNT heights throughout the sample, with shorter CNTs in the middle, having less access to gases. As height differences between the center and peripheries escalate, sample centers may collapse under the tension. The limited accessibility of the center is manifested also in inhomogeneous oxygen contents, between sample centers and peripheries. Finally, a sharp transition in deposition quality occurs during the deposition process of Al2O3, from homogeneous to inconsistent, which is also linked to the accessibility differences between. Adjusting process parameters, we have successfully coated 1.8 mm-tall VACNT arrays with a homogeneous thin (few nm) Al2O3 layer and were able to increase the depth at which, thick (few dozens of nm) Al2O3 coating is uniform from 20 to 350 μm. However, when VACNTs were functionalized, the penetration depth was found to correlate negatively with center oxygen content. These results, indicating diffusion as a rate-setting step in complex topography coatings, can significantly improve deposition quality and enhance the performance of thin-film applications such as membranes, sensors, and electrodes for energy harvesting and storage. [ABSTRACT FROM AUTHOR]