A Cobalt Sunrise: Thermites Based on LiClO4-Filled Co(0) Aerogels Prepared from Polymer-Cross-Linked Cobaltia Xerogel Powders.

A new route to metallic aerogels that bypasses the use of supercritical fluids and handling fragile wet-gel and aerogel precursors is exemplified by the carbothermal synthesis of monolithic Co(0) aerogels from compressed cobaltia xerogel powders coated conformally (cross-linked) at the primary particle level with a carbonizable polyurea. Residual carbon is removed, and carbon-free samples are obtained by high-temperature treatment of as-prepared Co(0) aerogels under a flowing stream of H2O/H2 that prevents oxidation of the Co(0) network. The durability of Co(0) aerogels is demonstrated under harsh processing conditions in their application as thermites. For this, Co(0) aerogel discs are infiltrated with LiClO4 from a melt and are ignited at about 1100 °C with an electric resistor. As Co(0) "burns" to CoO, temperature exceeds 1500 °C, and the heat released (-552 ± 2 kcal mol-1) is near to both the theoretical value (-58.47 kcal mol-1) and that from well-known pressed-pellet iron/perchlorate thermites (-66.6 kcal mol-1). The advantage of nanostructured thermites based on Co(0) aerogels is the efficiency (100%) by which the metal is consumed during its reaction with LiClO4 filling the pores.