2D Honeycomb Structure Research Articles

Processing of Al2O3/SiC ceramic cake preforms and their liquid Al metal infiltration

In order to prepare ceramic preforms, chemical processes were used rather than using mixing of ceramic powders to obtain porous Al 2 O 3 /SiC ceramic foams. A slurry was prepared by mixing aluminium sulphate and ammonium sulphate in the water, and silicon carbide powder was added into the slurry so that a uniform mixture of Al 2 O 3 /SiC cake could be produced. The resulting product was (NH 4 ) 2 SO 4 ·Al 2 (SO 4 ) 3 ·24H 2 O plus silicon carbide particles (SiC p ) after dissolving chemicals in the water. This product was heated up in a ceramic crucible in the furnace. With the effect of heat it foamed and Al 2 O 3 /SiC cake was obtained. Resulting Al 2 O 3 grains were arranged in a 3D honeycomb structure and the SiC particles were surrounded by the alumina grains. Consequently, homogeneous powder mixing and porosity distribution were obtained within the cake. The morphology of the powder connections was networking with flake like particles. These alumina particles resulted in large amounts of porosity which was desired for ceramic preforms to allow liquid metal flow during infiltration. The resulting high porous ceramic cake (preform) was placed in a sealed die and liquid aluminium was infiltrated by Ar pressure. The infiltration was achieved successfully and microstructures of the composites were examined.

Novel Approach to the Fabrication of Macroporous Polymers and Their Use as a Template for Crystalline Titania Nanorings

This paper presents a novel method for fabricating two- and three-dimensional (2D/3D) polymer macroporous structures and demonstrates their use as templates for the production of crystalline titania nanorings. 2D honeycomb and 3D inverse opal structures were fabricated with a linear shrinkage of about 1% by means of the selective dissolution of a sintered colloid crystal. In this novel method, the conventional infiltration step that introduces a polymer precursor prior to selective dissolution is not required. Honeycomb or isolated polymer rings can also be produced using this approach, depending on the sintering conditions. The resulting macroporous structures were used in this study as templates for the formation of isolated or interconnected crystalline titania nanorings via the calcination of titanium alkoxide deposited on the templates. The resulting titania nanorings exhibited a robust, undisrupted rutile phase.