Search

The piezoresistive behavior of polymer-derived amorphous SiAlCO ceramic is studied in a temperature range of 25-300 °C. It is shown that the material exhibits a giant gage factor of 7000-16,000, much higher than that for any reported high-temperature materials. The result also reveals that the material exhibits a positive temperature-dependent piezoresistive stress coefficient within the temperature range. The unusual piezoresistivity of the material was attributed to the structure of the SiAlCO, which consists of highly disordered graphene-like carbon nanoclusters dispersed within an amorphous matrix comprising of SiCO tetrahedra. The huge piezoresistivity, together with the processibility and low-cost, make the material very promising for high-temperature sensor applications. [ABSTRACT FROM AUTHOR]

The water spray systems are effective protection systems in the confined or unconfined spaces to avoid the damage to building structures since the high temperature when fires occur. NFPA 15 and 502 have suggested respectively that the factories or vehicle tunnels install water spray systems to protect the machinery and structures. This study discussed the cooling effect of water spray systems in experimental and numerical analyses. The actual combustion of woods were compared with the numerical simulations. The results showed that although the flame continued, the cooling effects by water spraying process within 120 seconds were obvious. The results also indicated that the simulation results of the fifth version Fire Dynamics Simulator (FDS) overestimated the space temperature before water spraying in the case of the same water spray system. [ABSTRACT FROM AUTHOR]

Abstract: The electric conductivity of polymer-derived SiBCNs pyrolyzed at different temperatures was studied. We showed that the boron impeded the graphitization of the free-carbon phase in the SiBCN, leading to a higher characteristic temperature and activation energy as compared to the SiCN. Such an impeding effect is due to the interaction between h-BN and graphite phase. We also provided a credible evidence to show that the increase in the electric conductivity of the SiBCN with pyrolysis temperature is likely due to the increase in the conductivity of the free-carbon phase. [Copyright &y& Elsevier]