Aerogel and Sol-Gel Composites Nanostructured Pyrophoric Materials

Decoy materials of this composition undergo the above reaction to reach temperatures of 820°C in less than one second and above 750°C for twelve secrmds after their exposure to air. Presently this type of material is used in a commercial decoy flare that is composed of pyrophoric iron coated onto steel foil articles [35]. Due to increasingly demanding materials performance, environmental standards, aging, and duty-cycle, there exists a need for continued development of new materials and approaches to achieve pyrophoric materials with tailorable output. 

Sine sol-gel synthesis is a bottom-up approach, the homogeneous incorporation of various dopants and additives in, for example, mixed composition materials is relatively facile and has been demcaistrated numerous times. This attribute is especially important to pyrotechnics as additives to modify the reactivity, spectral, or thermal output are a necessity [36,37]. 

There have been several reports of applying sol-gel materials and techniques to the formulatiOTi of nanostructured pyrophoric materials. The application of sol-gel materials to this technology area has involved three different approaches, which include (1) use of the aerogel as a framework for the deposition of pyrophoric materials (2) direct transformation of the aerogel skeleton itself (metal oxide) to a pyrophoric or easily combustible article and (3) use of an aerogel network as a reactive template for the reduction of a second sol-gel metal oxide phase to a pyrophoric or readily combustible material. 

Powders from commercial sources, different phases of iron oxides, as well as sol-gel-derived aerogels and xerogels were evaluated by the TGA method. According to the results the iron (III) oxide aerogel reduced to metallic iron the most rapidly under constant conditions (1 1 v/v, H2/Ar at 450°C). This is possibly related to the extremely high surface 

While not pyrophoric, the porous copper metal monolith is readily combustible by the application of a flame in air. In addition to copper, this method has been appUed to prepare other nanoporous metals such as iron, cobalt, nickel, and tin, as well as carbides of chromium, titanium, and hafnium (Chap. 14). This method is especially powerful as it appears to be applicable to a wide variety of metals and affords articles that are mrmolithic. 

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