New Materials for Environmental Applications:Thermoelectrics and Low-Temperature Oxidation Catalysts
Doctoral thesis, 2007

New materials have been researched for environmental applications as thermoelectrics and low-temperature oxidation catalysts. One of the main objectives of this thesis was to prepare and characterize new efficient thermoelectric materials (TM’s). Large single crystals of the phonon-glass electron-crystal (PGEC) material clathrate Ba8Ga16Ge30 was grown for the first time using the Czochralski method. For n-doped clathrate Ba8Ga16Ge30, thermoelectric evaluations showed a record high figure-of-merit, ZT above 800 K and evidence of a transition from extrinsic to intrinsic semiconductor behaviour with increasing temperature. Furthermore, a series of seven samples of YMn4+xAl8-x (-2.0 £ x £ 2.5) was prepared and evaluated for thermoelectric performance. Evaluation of the YMn4+xAl8-x samples showed that structurally ordered YMn4Al8 exhibits metallic conductivity, whereas off-stoichiometric compounds displayed semiconductor-like behavior at low temperatures. The second objective of this thesis was to evaluate new catalyst materials for low-temperature oxidation reactions. Hexagonal phase mesoporous Pt particles (H1-Pt) expose mainly concave surfaces with expected different catalytic properties compared to conventional Pt particles with convex surfaces. A series of Pt/Al2O3 catalysts was prepared using H1-Pt, Pt-black and wet-impregnated Pt. The catalysts were evaluated for CO oxidation. The H1-Pt/Al2O3 catalyst appeared less sensitive to CO poisoning but more sensitive to mass-transport limitations than the other two catalysts. Finally, a study of catalysts for selective CO oxidation in a hydrogen-rich feed gas stream was performed in a high throughput screening system. The study showed that Pt/Al2O3 and Rh/Al2O3 catalysts were most active and selective for CO oxidation in the presence of H2.

selective oxidation




heterogeneous catalysis


noble metals


phonon glass-electron crystal

figure-of-merit (ZT)

10-an, Kemigården 4, Chalmers, Göteborg
Opponent: Professor Reine Wallenberg, Lunds Universitet, Lund


Ali Saramat

Competence Centre for Catalysis (KCK)

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Subject Categories

Other Materials Engineering



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 2587

10-an, Kemigården 4, Chalmers, Göteborg

Opponent: Professor Reine Wallenberg, Lunds Universitet, Lund

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