Sum-frequency vibrational spectroscopy in the OH stretch region was employed to study structures of water/ -Al 2 O 3 (0001) interfaces at different pH values. Observed spectra indicate that protonation and deprotonation of the alumina surface dominate at low and high pH, respectively, with the interface positively and negatively charged accordingly. The point of zero charge (p.z.c.) appears at pH ~6.3, which is close to the values obtained from streaming potential and second harmonic generation studies. It is significantly lower than the p.z.c. of alumina powder. The result can be understood from the pK values of protonation and deprotonation at the water/ -Al 2 O 3

Laser-ablated group IV metal atoms have been co-deposited at 11 K with water molecules in excess argon. The metal atoms reacted with water to form the insertion product HMOH and H 2 M(OH) 2 (M ) Ti, Zr, Hf) molecules spontaneously. Photolysis of the HTiOH species produced the H 2 TiO molecule as well as the TiO monoxide. In the cases of Zr and Hf, however, the H 2 ZrO and H 2 HfO molecules were produced on annealing, and the H 2 elimination process was not observed on photolysis. In addition, the HMO species were also observed and identified. The aforementioned species were identified via isotopic substitutions as well as theoretical frequency calculations. Qualitative analysis of the possible reaction paths leading to the observed products is proposed.

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The thermal and electrical transport properties of various spark plasma-sintered HfB 2 -and ZrB 2 -based polycrystalline ceramics were investigated experimentally over the 298-700 K temperature range. Measurements of thermal diffusivity, electrical resistivity, and Hall coefficient are reported, as well as the derived properties of thermal conductivity, charge carrier density, and charge carrier mobility. Hall coefficients were negative confirming electrons as the dominant charge carrier, with carrier densities and mobilities in the 3-5 Â 10 21 cm À3 and 100-250 cm 2 . (V . s) À1 ranges, respectively. Electrical resistivities were lower, and temperature coefficients of resistivity higher, than those typically reported for HfB 2 and ZrB 2 materials manufactured by the conventional hot pressing. A Wiedemann-Franz analysis confirms the dominance of electronic contributions to heat transport. The thermal conductivity was found to decrease with increasing temperature for all materials. Results are discussed in terms of sample morphology and compared with data previously reported in the scientific literature.