Effect of Polymer Removal on the Morphology and Phase of the Nanoparticles in All-Inorganic Heterostructures Synthesized via Two-Step Polymer Infiltration

Polymer templates play an essential role in the robust infiltration-based synthesis of functional multicomponent heterostructures with controlled structure, porosity, and composition. Such heterostructures are be used as hybrid organic–inorganic composites or as all-inorganic systems once the polymer templates are removed. Using iron oxide/alumina heterostructures formed by two-step infiltration of polystyrene-block-polyvinyl pyridine block copolymer with iron and aluminum precursors from the solution and vapor-phases, respectively, we show that the phase and morphology of iron oxide nanoparticles dramatically depend on the approach used to remove the polymer. We demonstrate that thermal and plasma oxidative treatments result in iron oxide nanoparticles with either solid or hollow morphologies, respectively, that lead to different magnetic properties of the resulting materials. Our study extends the boundaries of structure manipulations in multicomponent heterostructures synthesized using polymer infiltration synthesis, and hence their properties.

Performance analysis and comparison of methyl-modified Al2O3/SiO2 xerogels fabricated by two methods

Two methyl-modified Al2O3/SiO2 xerogels, i. e. AIP-Al2O3/MSiO2 and ANN-Al2O3/MSiO2 xerogels, were prepared using aluminum isopropoxide and aluminum nitrate nonahydrate as the aluminum precursors, respectively. The appearance, density, viscosity, Gibbs activation energy for viscous flow and reaction rate constant of the sols were analyzed and compared. Their microstructures were characterized by means of powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen adsorption–desorption measurements. The results show that the Al–O–Si bond is formed in the AIP-Al2O3/MSiO2 and ANN-Al2O3/MSiO2 xerogels. The ANN-Al2O3/MSiO2 sol has a smaller mean particle size and greater sol stability than the AIP-Al2O3/MSiO2 sol. Meanwhile, the ANN-Al2O3/MSiO2 xerogel has a smaller pore size and higher porosity. The total pore volume and specific surface area of the ANN-Al2O3/MSiO2 xerogel are 27.27% and 29.36% larger than those of the AIP-Al2O3/ MSiO2 sample, respectively. The saturated adsorption capacity of the ANN-Al2O3/MSiO2 xerogel to methylene blue is 7.15% larger than that of the AIP-Al2O3/MSiO2 xerogel.

Fischer–Tropsch synthesis over alumina-supported cobalt catalysts: effects of different spray temperature of aluminum slurry

Aluminum slurry was obtained by precipitating Al(NO3)3·9H2O and ammonium carbonate, and the slurry was dried by adopting spray means. The effects of different spray temperature on the as-synthesised aluminum precursors, calcined alumina, and the supported cobalt catalysts were investigated by the characterizations of SEM, XRD, TG-DTA, H2-TPD, H2-TPR, etc., and the activity and stability of the as-prepared catalysts for Fischer–Tropsch synthesis were also studied. It indicated that the aluminum precursor spray dried at 250 °C exhibited homogeneous microspheres, the calcined alumina exhibited single-particle size distribution and monomodal pore distribution, and the corresponding supported cobalt catalyst possessed proper cobalt particles (6.4 nm), which was benefitial for acquiring a high conversion rate (the turnover frequency is 17.2 × 10−3/s) and excellent stability (the deactivation rate is 0.31%) for Fischer–Tropsch synthesis.

Aerosol-assisted synthesis of mesoporous aluminosilicate microspheres: the effect of the aluminum precursor

Spray-dried mesoporous aluminosilicates, with spherical morphology, high surface area and accessible porosity, have been synthesized under mild acidic aqueous conditions by using different aluminum precursors.