Aligned porous substrates by directional melting and resolidification

#The present invention relates generally to the templated growth of porous or non-porous castings, and more specifically to the formation of porous or non-porous castings via localized melting and directional re-solidification within a honeycomb substrate.

#Porous substrates can be used in a wide variety of applications including catalysis, filtration, membranes, etc. And while numerous processing techniques such as extrusion and foaming have been developed to produce porous and other cellular materials, it remains difficult during processing to precisely and efficiently control the size, shape, directionality, isotropy (or anisotropy), connectivity and tortuosity of the porosity and/or the cellular structure. An additional challenge in forming cellular materials relates to the ubiquitous use of pore forming agents and the difficulties associated with removing them from the final product.

#Non-porous substrates comprising crystalline metals (e.g., Cu) and semiconductors (e.g., Si, GaAs, etc.) can be used in both semiconductor and non-semiconductor applications. For example, ingots of polycrystalline silicon can be prepared for photovoltaic applications via directional solidification in quartz crucibles as an alternative to Czochralski (CZ) growth. In addition to semiconductor materials, directional solidification can also be used to form metallic and ceramic substrates. As used herein, a substrate is a material upon which a process is conducted, or upon which a device or structure is constructed.

#FIG. 1 is a schematic illustration of a localized heater coil directional solidification apparatus; and

#FIG. 2 is a schematic drawing depicting aspects of directional solidification.

#A method of forming a templated casting comprises incorporating a liquid feedstock into the channels of a honeycomb substrate to form a feedstock-laden substrate, solidifying the liquid feedstock within the channels, locally melting the solidified feedstock to form liquid pools, and directionally re-solidifying the melt.

#Prior to solidifying the liquid feedstock, the liquid feedstock can comprise a single-component liquid (e.g., single phase or multi-phase) or a multi-component liquid (e.g., single phase or multi-phase). Table 1 sets forth example feedstocks suitable for forming a templated casting.

#TABLE 1 Example Single- and Multi-Component Feedstocks Single Component Multi-Component Single Phase Si, Cu, Ge, water Si + Ge, Ga + As, silicic acid + water, PVA + water Multi-Phase slush alumina + PVA + water