Synthesis, characterization and evaluation of unsupported porous NiS2 sub-micrometer spheres as a potential hydrodesulfurization catalyst

Three-dimensional crystals of air spheres in titania (TiO2) with radii between 120 and 1000 nanometers were made by filling the voids in artificial opals by precipitation from a liquid-phase chemical reaction and subsequently removing the original opal material by calcination. These macroporous materials are a new class of photonic band gap crystals for the optical spectrum. Scanning electron microscopy, Raman spectroscopy, and optical microscopy confirm the quality of the samples, and optical reflectivity demonstrates that the crystals are strongly photonic and near that needed to exhibit band gap behavior.

Titania, zirconia, and alumina samples with periodic three-dimensional arrays of macropores were synthesized from the corresponding metal alkoxides, using latex spheres as templates. In a fast, single-step reaction, the monomeric alkoxide precursors permeate the array of bulk polystyrene spheres and condense in air at room temperature. Close packed, open-pore structures with 320- to 360-nanometer voids are obtained after calcination of the organic component at 575 degreesC. The examples presented demonstrate the compositional diversity possible with this technique. The resulting highly structured ceramics could have applications in areas ranging from quantum electronics to photocatalysis to battery materials.