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Thermoelectric properties of alkali activated aluminosilicates
Filipská, Kristýna ; Fiala,, Lukáš (referee) ; Zmeškal, Oldřich (advisor)
This work focuses on the potential usage of alkali-activated aluminosilicates (AAA) in relation to energy harvesting. It sets a goal of familiarizing the reader with thermoelectrical conversion itself and its existence within those materials. Based on this knowledge, the measurement of thermoelectrical voltage has been conducted in chosen mixtures of AAA; more specifically a slag geopolymer with carbon black admixture, a slag geopolymer with graphite powder admixture and a metashale geopolymer with graphite powder admixture. This experiment was executed by repeated heating of the surface area of the sample on one side using a resistor, while the other side was kept at reference temperature. The response in the form of voltage generated in the sample as well as on the electrodes was recorded. The measured values were then used to calculate the Seebeck coefficient. The best response was provided by a slag geopolymer sample with carbon black admixture at 4 % concentration (|| = 1904 V/K). The second goal was to measure thermal properties of those samples, specifically the specific heat capacity, the thermal conductivity coefficient and thermal diffusivity. This goal has been reached by capturing the samples with a thermal camera while heating them on a hot-plate. The highest values of specific heat capacity and the thermal conductivity coefficient were provided by a sample of metashale geopolymer with graphite powder admixture at 8 % concentration (c = 2086 J/kg/K; = 1,815 W/m/K). Thermal diffusivity proved to be almost identical in all samples, 610-7 m2/s on average. Based on the results, we conclude that the thermoelectrical conversion in these materials is not enough to be significant in bigger scale energy harvesting yet. However, we also believe that it’s possible to reach better results with further research.
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