The reversible Mg
2FeH
6 and the mixed Mg
2FeH
6–MgH
2 hydride systems
Eqs. (1) and (2) turned out to be highly suitable materials for thermochemical thermal energy storage at around 500
°C, for ...example as the storage of solar or excess industrial heat. The systems are characterized by a high gravimetric and volumetric thermal energy density in comparison to sensible or latent heat storage materials (
Table 1) and have excellent stability in cycle tests. Further advantages include low price of the starting materials, a free choice and constancy of the heat delivery temperature by controlling the applied hydrogen pressure, and the absence of heat losses with time. By means of combined TEM–EDX investigations essential features of the initial formation and the subsequent de- and rehydrogenation processes of Mg
2FeH
6 could be elucidated on a micro- or nanoscale level.
Casting silica nets: By repeated “nanocasting” it is possible to first obtain a negative of the SBA‐15 structure, known as CMK‐3, which is then used to produce another nanocast by impregnation with ...tetraethoxysilane and condensation. After calcination to remove the carbon, an ordered mesoporous silica is obtained, called NCS‐1 (see scheme). This pathway could be generalized to allow also the synthesis of other ordered oxides.
The preparation, characterization, and catalytic properties of Pd nanoparticles supported on mesoporous organic–inorganic hybrid materials are described for continuous-flow aerobic oxidation of ...alcohols using supercritical carbon dioxide (scCO
2) as a mobile phase. The nanoparticles were generated “bottom-up” from molecular precursors that were precoordinated to the support through suitable anchor units. The most active material allows high single-pass conversions in scCO
2 at temperatures as low as 60 °C. This high activity may be associated with the presence of small primary crystallites (approx. 2 nm) that conglomerate to ensembles about 25 nm in size, leading to a larger number of high-indexed planes in small volume units. These findings may provide useful guidelines for further catalyst design on the nanoscale for green oxidation methods.
Nanocast silica (NCS‐1) was synthesized by a casting process by employing the mesoporous carbon CMK‐3 (the replica of SBA‐15) as a template, tetraethoxysilane (TEOS) as the silica source, and ...hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS‐1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA‐15 used for the synthesis of CMK‐3 over two replication steps on the nanometer scale. This demonstrates the well‐connected porosity in CMK‐3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS‐1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS‐1 can be tuned to a certain range by varying these parameters.
Nanostructured silica from carbon: Nanocast silica (NCS‐1) was synthesized by a nanocasting process using the mesoporous carbon CMK‐3, the replica of SBA‐15, as a template (see picture for a schematic illustration). The ordered carbon template was removed by employing different methods. The ordered structure, with hexagonal symmetry and the morphology of the original SBA‐15, was maintained over two replication steps on the nanometer scale.
Ordered, mesoporous cobalt oxide was synthesized via a nanocasting pathway from organically modified large-pore Ia3d silica. A replica structure could be obtained, which shows weak magnetic ordering ...at low temperatures due to the small size of the individual Co3O4 domains forming the mesostructure.
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