Thermoelectric and Mechanical Properties of SiC+SWCNTs+B4C Nanocomposites with Sol-gels Diffusion

Thermoelectric (TE) and mechanical properties of Single wall carbon nanotubes (SWCNTs) and Boron Carbide reinforced Silicon carbide (SiC) nanocomposites were experimentally evaluated after doping through the sol-gel diffusion technique. The samples were produced with a high temperature (1550o C) sintering process. For sol-gel diffusion, a Boron-Antimony combination was used. Boron (B) was a Ptype and Antimony (Sb) was an N-type dopant. Hot and cold junctions were created using silver epoxy and Alumel (Ni-Al) wire, and thermoelectric tests were conducted. The carbon nanotubes used were approximately 60% semiconducting and 40% metallic. Voltage (mV) was measured for different categories of samples against temperature difference (∆T). Control SiC samples showed no TE effect at pristine form, but when infused with SWCNTs, a TE effect was present. The TE effect of the nanocomposite samples increased substantially with Boron-Antimony sol-gel diffusion. The Seebeck coefficient increased to 1.2 mV/ oC. Three point bending tests of the nanocomposites samples showed an interesting plateau in the flexure stress-strain curves. The structure-property relation was analyzed using SEM (scanning electron microscope) and EDS (Energy dispersive spectroscopy). It was revealed that fiber-like SWCNTs created a randomly distributed network, and Nano bridges inside the SiC matrix and enhanced the thermoelectric and mechanical properties of the nanocomposites.