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Manuscript Click here to download Manuscript AeroSic-Paper_JSST_30.docx Click here to view linked References HIGHLIGHTS • Homogeneous SiO2-carbon nanotube monolithic aerogels were obtained by rapid controlled gelation • The carbon nanotubes were homogeneously dispersed in the highly porous silica matrix • The hybrid aerogels kept outstanding structural features and densities below 80 mg/cm in all cases • The Si-O-C covalent bonding between carbon nanotubes and silica matrix was prompted by FTIR • The carbon nanotubes turned the aerogels into 100% stiffer and 60% more deformable materials ABSTRACT This work introduces a new synthesis procedure for obtaining homogeneous silica hybrid aerogels with carbon nanotube contents up to 2.50 wt.%. The inclusion of nanotubes in the highly porous silica matrix was performed by a two-step sol-gel process, resulting in samples with densities below 80 mg/cm 3. The structural analyses (N2 physisorption and SEM) revealed the hierarchical structure of the porous matrix formed by nanoparticles arranged in clusters of 100 nm and 300 nm in size, specific surface areas around 600 m 2 /g and porous volumes above 4.0 cm 3 /g. In addition, a relevant increase on the mechanical performance was found, and an increment of 50% for the compressive strength and 90% for the maximum deformation were measured by uniaxial compression. This reinforcement was possible thanks to the outstanding dispersion of the CNT within the silica matrix and the formation of Si-O-C bridges between nanotubes and silica matrix, as suggested by FTIR. Therefore, the original synthesis procedure introduced in this work allows the fabrication of highly porous hybrid materials loaded with carbon nanotubes homogeneously distributed in the space, which remain available for a variety of technological applications.

The effect of the incorporation ofNH4+into the CH3NH3+sites of the tetragonal perovskite CH3NH3PbI3is analysed. Also, how it affects the introduction of Cd2+cations into Pb2+sites for a perovskite with 25 at.% ofNH4+is addressed. The incorporation ofNH4+into perovskite leads to a dramatic loss of crystallinity and to the presence of other phases. Moreover, the NH4PbI3was not found. The less formation of perovskite whenNH4+is incorporated is due to geometrical factors and not changes in the chemical state bonding of the ions. Also, the samples where perovskite is formed show similar band gap values. A slight increase is observed for samples withx=0.5and 0.75. For the sample withx=1, a drastic increase of the band gap is obtained. Periodic-DFT calculations agree with the experimental structural tendency whenNH4+is incorporated and the density of states analysis confirmed the experimental band gap. The perovskite with 25 at.% ofNH4+was selected for studying the effect of the concentration of Cd on the structural and electronic properties. The theoretical band gap values decreased with the Cd concentration where the narrowing of Cd s-states in the conduction band plays an important role.

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