Nanomaterials in Cementitious Composites: An Update

This review is an update about the addition of nanomaterials in cementitious composites in order to improve their performance. The most common used nanomaterials for cementitious materials are carbon nanotubes, nanocellulose, nanographene, graphene oxide, nanosilica and nanoTiO2. All these nanomaterials can improve the physical, mechanical, thermal and electrical properties of cementitious composites, for example increase their compressive and tensile strength, accelerate hydration, decrease porosity and enhance fire resistance. Cement based materials have a very complex nanostructure consisting of hydration products, crystals, unhydrated cement particles and nanoporosity where traditional reinforcement, which is at the macro and micro scale, is not effective. Nanomaterials can reinforce the nanoscale, which wasn’t possible heretofore, enhancing the performance of the cementitious matrix.

Biomineral structure and crystallographic arrangement of cerioid and phaceloid growth in corals belonging to the Syringoporicae (Tabulata, Devonian–Carboniferous): a genetic reflection

An extensive study of the microstructure, nanostructrure and crystallographic properties of six taxa belonging to four different genera of Devonian and Carboniferous Syringoporicae showing dense phaceloid (Pleurosiphonella), pseudocerioid (Neomultithecopora) and cerioid growth patterns (Roemeria and Roemeripora) has been done in order to disclose the similarities and differences in the growth processes at the biomineral scale and understand the growth processes that provide organisms with an evolutionary advantage to colonize different habitats. All the skeletons have similarities regarding the biocrystallization process, showing that the Syringoporicae skeletons are a product of matrix-mediated biocrystallization. Micro- and nanotextural features are common in all of the skeletons studied, showing that they were composed of hierarchical structures. All studied taxa possess a complex nanostructure composed of co-oriented rounded nanocrystals with different sizes and morphologies, depending on the taxon. The identified microstructures include granules, lamellae, fibres and hyaline elements. The crystallographic techniques demonstrate that all of them except the hyaline elements are biogenic in origin. Granules could be aborted fibres during the growth of two corallites in contact. On the other hand, the study of the biomineral properties suggests that the skeleton structure is a reflection of the genetic code. The median lamina was formed by the joint crystallization of both polyps at the same time. The variation in the internal structural organization (phaceloid, pseudocerioid or cerioid) was conditioned by the environment (stressful situations or feeding strategies); on the contrary, the final structure is controlled by genetics and their crystallographic properties are characteristic for each internal structural organization.

Unravelling the complex nanostructure of La0.5−xLi0.5−xSr2xTiO3 Li ionic conductors

The intricate nanostructure of La0.5−xLi0.5−xSr2xTiO3 Li-ion conductors has been elucidated. Advanced transmission electron microscopy has allowed investigation where average structure models cannot account for the changeable local atomic arrangements detected.

Mapping the morphological changes of deposited gold nanoparticles across an imprinted groove

The gradient gold layer morphology below the percolation threshold along a channel groove imprinted into a pressure-sensitive adhesive polymer film is studied. In order to elucidate the complex nanostructure of the sputter-deposited gold nanoparticle layer, nanobeam grazing-incidence small-angle X-ray scattering and imaging ellipsometry are used. Thus, the complex nanostructure of this metal–polymer nanocomposite can be detected, distinguished and identified. The presence of macroscopically curved structures, as introduced by the imprinted ridges, can cause deviations from the mean metal nanoparticle morphology, probed on the `flat' sample area outside the ridges. The phase-separated morphology of the polymer film is rather unaffected by the imprint structure but leads, in addition, to a selective growth of gold on polystyrene-rich domains.