Galvanic porous silocon composites for nanoenergetics and monolithically integrated ignitor

Abstract

Porous silicon (PS) films composed of pores with diameters less than 3 nm are fabricated using a galvanic etching approach that does not require an external power supply. A highly reactive, nanoenergetic composite is then created by impregnating the nanoscale pores with the strong oxidizer, sodium perchlorate (NaClO4). The combustion propagation velocity of the energetic composite is measured using microfabricated diagnostic devices in conjunction with high-speed optical imaging up to 930,000 frames per second. Combustion velocities averaging 3,050 m / s are observed for PS films with specific areas of ˜840 m2 / g and porosities of about 65-67%. Galvanic etching may also be used to fabricate other porous silicon morphologies and also strong oxidizers other than NaClO4 could be used to create a nanoenergetic porous silicon composite.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application No. 61 / 569,893 filed on Dec. 13, 2011, the complete disclosure of which, in its entirety, is herein incorporated by reference.GOVERNMENT INTEREST[0002]The invention was made in part under Army Research Office grant W911NF-06-1-0342 to the University of Colorado under which the Government has certain rights. The embodiments described herein may be manufactured, used, sold, imported and / or licensed by or for the United States Government without the payment of royalties thereon.BACKGROUND[0003]1. Technical Field[0004]The invention herein generally relates to a method of making a nanoenergetic device with an integrated ignitor based on porous silicon formed by a galvanic cell.[0005]2. Description of the Related Art[0006]Porous silicon (PS) is a widely studied material with applications for fuel cells, solar cells, and biology. The large specific surface area resulting f...

AI Technical Summary

Benefits of technology

The patent describes a process for making a device with a built-in ignitor using porous silicon formed by a chemical reaction. The process involves depositing a layer of metal on a silicon substrate and then immersing it in a solution to etch the silicon. The resulting device has a controlled ignition mechanism that can be used to initiate a reaction.

Problems solved by technology

The large specific surface area resulting from the nanometer scale pores within the PS structure yields a highly reactive material that is especially susceptible to oxidation.

However, the conventional formation of PS requires the etching of Si with hydrofluoric (HF) acid based electrolyte in a custom Teflon etch cell using an external power supply, an approach not well suited for batch processing.

Additionally, the conventional technique is very destructive to metal films on the substrate, greatly limiting the processing options for integration with electronics and MEMS.

A commonly owned and pending patent application Ser. No. 12 / 535,141 filed on Aug. 4, 2009, presented a workaround to the aggressive nature of the etch and devices were made with this method, but it was a difficult process to practice.

Since the galvanic etch rate is much slower near gold than platinum, the silicon etch near the exposed gold of the ignitor wire is not very aggressive and the wire is undamaged during etching.

On the contrary, in the electrochemical etching technique, the ignitor wire was shown to occasionally fail as the porous silicon would crack.

Images