Carbon Fiber-Silica Aerogel Composite with Enhanced Structural and Mechanical Properties Based on Water Glass and Ambient Pressure Drying

Abstract

The article presents the synthesis of silica aerogel from a much cheaper precursor of water glass that was reinforced with short pitch carbon fiber by way of ambient pressure drying. Before being added to the silica gel, the carbon fibers were surface modified to increase adhesion at the interfacial border. We were able to obtain stable structures of the composite with the amount of fibers above 10% by volume. The presence of fibers in the silica matrix resulted in lower synthesis time of the composite, improved adhesion of fibers to the aerogel nanostructure, and increased mechanical and structural parameters. An additional effect of the presence of fibers in excess of 10% by volume was a new function of the nanocomposite-the ability to conduct electric current. The most optimal parameters of the composite, however, were obtained for silica aerogel reinforced with 10 vol.% of carbon fibers. This material indicated relatively low density and good physical parameters. The paper also analyzes the results on the synthesis of fiber-reinforced silica aerogels that have appeared in recent years and compares these to the results gained in presented work.

Keywords: ambient pressure drying APD; carbon microfibers: structural and mechanical properties; silica aerogel; water glass.

Figure 1

Most frequently used ways of reinforcing the structure of silica aerogels.

Figure 2

Synthesis of the silica aerogel–carbon fibers composite.

Figure 3

FTIR analysis curves obtained for silica aerogel and its carbon fiber composites in relation to the amount of fibers (precursor 10% solution of water glass, APD).

Figure 4

Thermogravimetric curves obtained for silica aerogel and its composites with carbon fibers in relations to the amount of fibers (precursor 10% solution of water glass, APD).

Figure 5

Stress-strain and stress-displacement curves obtained for AG 10% CF (a,b) and for AG 15% CF (c,d), respectively.

Figure 6

(a) SEM characterization for AG 10% CF composite, (b) bridging of silica aerogel by carbon fiber.

Figure 7

(a) Adhesion of silica aerogel to carbon fiber, (b) boundary between silica aerogel and carbon fiber.

Figure 8

(a) SEM characterization of AG 10% CF before loading, (b) and after loading, (c) microcracking of silica aerogel structure reinforced with carbon fiber, (d) enlargement of silica aerogel microcracks.